[formrecognizer] update links (#21016)

* update with migration guide links

* update links in changelog

* fix changelog links

sdk/formrecognizer/azure-ai-formrecognizer/CHANGELOG.md

@@ -4,7 +4,7 @@
 
 This version of the SDK defaults to the latest supported API version, which currently is v2021-09-30-preview.
 
-> Note: Starting with version 2021-09-30-preview, a new set of clients were introduced to leverage the newest features of the Form Recognizer service. Please see the Migration Guide for detailed instructions on how to update application code from client library version 3.1.X or lower to the latest version. Also, please refer to the README for more information about the library. 
+> Note: Starting with version 2021-09-30-preview, a new set of clients were introduced to leverage the newest features of the Form Recognizer service. Please see the [Migration Guide](https://github.com/Azure/azure-sdk-for-python/tree/main/sdk/formrecognizer/azure-ai-formrecognizer/MIGRATION_GUIDE.md) for detailed instructions on how to update application code from client library version 3.1.X or lower to the latest version. Also, please refer to the [README](https://github.com/Azure/azure-sdk-for-python/tree/main/sdk/formrecognizer/azure-ai-formrecognizer/README.md) for more information about the library. 
 
 ### Features Added
 - Added new `DocumentAnalysisClient` with  `begin_analyze_document` and `begin_analyze_document_from_url` methods. Use these methods with the latest Form Recognizer 

sdk/formrecognizer/azure-ai-formrecognizer/README.md

@@ -39,7 +39,7 @@ This table shows the relationship between SDK versions and supported API version
 |3.0.0| 2.0
 
 > Note: Starting with version 2021-09-30-preview, a new set of clients were introduced to leverage the newest features
-> of the Form Recognizer service. Please see the Migration Guide for detailed instructions on how to update application
+> of the Form Recognizer service. Please see the [Migration Guide][migration-guide] for detailed instructions on how to update application
 > code from client library version 3.1.X or lower to the latest version. Additionally, see the [Changelog][changelog] for more detailed information.
 > The below table describes the relationship of each client and its supported API version(s):
 
@@ -607,6 +607,7 @@ This project has adopted the [Microsoft Open Source Code of Conduct][code_of_con
 [sdk_logging_docs]: https://docs.microsoft.com/azure/developer/python/azure-sdk-logging
 [sample_readme]: https://github.com/Azure/azure-sdk-for-python/tree/main/sdk/formrecognizer/azure-ai-formrecognizer/samples
 [changelog]: https://github.com/Azure/azure-sdk-for-python/tree/main/sdk/formrecognizer/azure-ai-formrecognizer/CHANGELOG.md
+[migration-guide]: https://github.com/Azure/azure-sdk-for-python/tree/main/sdk/formrecognizer/azure-ai-formrecognizer/MIGRATION_GUIDE.md
 
 [cla]: https://cla.microsoft.com
 [code_of_conduct]: https://opensource.microsoft.com/codeofconduct/

sdk/formrecognizer/azure-ai-formrecognizer/samples/README.md

@@ -12,7 +12,7 @@ urlFragment: formrecognizer-samples
 # Samples for Azure Form Recognizer client library for Python
 
 > Note: Starting with version 2021-09-30-preview, a new set of clients were introduced to leverage the newest features
-> of the Form Recognizer service. Please see the Migration Guide for detailed instructions on how to update application
+> of the Form Recognizer service. Please see the [Migration Guide][migration-guide] for detailed instructions on how to update application
 > code from client library version 3.1.X or lower to the latest version. Additionally, see the [Changelog][changelog] for more detailed information.
 
 These code samples show common scenario operations with the Azure Form Recognizer client library.
@@ -105,6 +105,7 @@ what you can do with the Azure Form Recognizer client library.
 [get-key-instructions]: https://github.com/Azure/azure-sdk-for-python/blob/main/sdk/formrecognizer/azure-ai-formrecognizer/README.md#get-the-api-key
 [changelog]: https://github.com/Azure/azure-sdk-for-python/blob/main/sdk/formrecognizer/azure-ai-formrecognizer/CHANGELOG.md
 [v3.0.0-samples-tag]: https://github.com/Azure/azure-sdk-for-python/tree/azure-ai-formrecognizer_3.0.0/sdk/formrecognizer/azure-ai-formrecognizer/samples
+[migration-guide]: https://github.com/Azure/azure-sdk-for-python/tree/main/sdk/formrecognizer/azure-ai-formrecognizer/MIGRATION_GUIDE.md
 
 <!-- V3.2-beta links -->