WT-17399 removed the s3_store extension source and most of its references, but three references were missed and remain on the WT-17398-cloud-storage-deprecation integration branch:

Affected files:

1. test/evergreen/evg_cfg.py (line 31) — "ext/storage_sources/s3_store/test" still listed in make_check_subdir_skips; the directory no longer exists after WT-17399.

2. test/format/config.sh (line 380) — the tiered_storage.storage_source help string still lists s3_store as a valid value.

3. test/format/format_config_def.c — generated from config.sh; inherits the stale s3_store reference and must be regenerated after config.sh is fixed.

Work to do:

• Remove "ext/storage_sources/s3_store/test" from the make_check_subdir_skips list in test/evergreen/evg_cfg.py
• Remove s3_store from the help string for tiered_storage.storage_source in test/format/config.sh
• Regenerate test/format/format_config_def.c by running bash config.sh from test/format/
• Verify with:

  grep -rn "s3_store" test/evergreen/evg_cfg.py test/format/config.sh test/format/format_config_def.c

Branch: branch off WT-17398-cloud-storage-deprecation, PR targets WT-17398-cloud-storage-deprecation.