fix: jwe-decrypt secret length restriction

[Vacant2333]

Description

add restriction for jwe-decrypt plugin
the secret length should be 32 chars only, it will be checked on the check_scheme

Fixes #
#10883 (comment)

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible (If not, please discuss on the APISIX mailing list first)

[Vacant2333]

the previos ci was wrong, i will fix it on here 7052e25
the test 2 and 3 test for the value type of key and secert,

and i will remove the schema min length, because the length of secret will be checked on check_schema

[Vacant2333]

@kayx23 @shreemaan-abhishek can u help me take a look~~

[kayx23]

Suggested change

	After enabling `is_base64_encoded`, your `secret` length may exceed 32 chars. You only need to make sure that the length after Decode is still 32 chars.
	After enabling `is_base64_encoded`, your `secret` length may exceed 32 chars. You only need to make sure that the length after decoding is still 32 chars.

tbh i think this info should go into the description of secret, rather than a note at the bottom (if its not too difficult to read)

[Vacant2333]

if we add this description to secret it will be too long i think

[shreemaan-abhishek]

why change this test case?

[Vacant2333]

hi, i have explan this at here #10928 (comment), the test name was wrong, Test 3&4 was test for the wrong type of secret & key

[shreemaan-abhishek]

LGTM