Update arbitrum-docs/launch-orbit-chain/how-tos/customize-precompile.mdx

Co-authored-by: symbolpunk <103775631+symbolpunk@users.noreply.github.com>

arbitrum-docs/launch-orbit-chain/how-tos/customize-precompile.mdx

@@ -205,7 +205,7 @@ Now navigate to the [precompiles interface][precompile_interface_dir_link] direc
 event Hi(address caller);
 ```
 
-If you want to make the param in event as `index`, just add index to solidity interface as this:
+If you want to make the param in event as `index`, just add `index` to the Solidity interface:
 
 ```solidity
 event Hi(address indexed caller);