Remove the filesystem's connection= and pass client= to custom s3fs filesystem classes #1386

Use case

#1363 deprecates the connection= argument of S3FileSystem and AioS3FileSystem in favor of client= and retry_config= (#1378), and defers two breaking steps to the next major release.
This issue tracks those steps for 5.0.0.

Proposed change

1. Remove connection= from S3FileSystem and AioS3FileSystem (step 5 of Replace the filesystem's connection= with client= and retry_config= injection #1363).
   Passing it raises TypeError like any unknown argument.
   Remove the deprecation message, the deprecation warning path in S3FileSystem._resolve_injected_client, the tests for the warning, and the deprecation paragraph in docs/filesystem.md.
2. Change the keywords passed to the s3fs cursor's filesystem_class (step 6 of Replace the filesystem's connection= with client= and retry_config= injection #1363).
   A custom class is created with client, retry_config, default_block_size, and skip_instance_cache=True instead of connection, through pyathena.filesystem.s3_filesystem(), as S3FileSystem and AioS3FileSystem already are.
   No new factory hook.
   Update the two sentences in docs/s3fs.md that describe the current and next-major behavior.

Both are breaking changes and need release notes:

• Code that passes connection= must use pyathena.filesystem.s3_filesystem(connection), or client=connection.s3_client and retry_config=connection.retry_config.
• A custom filesystem_class must accept the client and retry_config keywords.

Validation plan (if implementing)

• Filesystem unit tests in tests/pyathena/filesystem/ for the removed argument.
• tests/pyathena/s3fs/test_result_set.py for the keywords a custom filesystem_class receives.
• The s3fs cursor integration tests for the default and async filesystem classes.