fix(ingest): tighten Source.create type annotations

[hsheth2]

Supersedes #8620

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable). If a new feature has been added a Usage Guide has been added for the same.
• For any breaking change/potential downtime/deprecation/big changes an entry has been made in Updating DataHub

[hsheth2]

the config_class decorator auto-generates this method, so we can just remove it here

[codecov]

Codecov Report

Attention: Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...ngestion/src/datahub/ingestion/source/demo_data.py	0.00%	1 Missing ⚠️

Files with missing lines	Coverage Δ
...data-ingestion/src/datahub/ingestion/api/source.py	99.15% <100.00%> (ø)
.../src/datahub/ingestion/source/delta_lake/source.py	92.00% <ø> (-0.21%)	⬇️
.../src/datahub/ingestion/source/fivetran/fivetran.py	94.54% <100.00%> (-0.20%)	⬇️
...ub/ingestion/source/kafka_connect/kafka_connect.py	92.15% <100.00%> (-0.20%)	⬇️
...ingestion/src/datahub/ingestion/source/metabase.py	85.30% <100.00%> (-0.19%)	⬇️
...a-ingestion/src/datahub/ingestion/source/mlflow.py	100.00% <ø> (ø)
...ata-ingestion/src/datahub/ingestion/source/nifi.py	89.95% <ø> (-0.07%)	⬇️
...a-ingestion/src/datahub/ingestion/source/redash.py	71.70% <ø> (+0.23%)	⬆️
...datahub/ingestion/source/snowflake/snowflake_v2.py	89.08% <ø> (-0.16%)	⬇️
...ingestion/src/datahub/ingestion/source/superset.py	80.13% <100.00%> (-0.27%)	⬇️
... and 2 more

... and 4 files with indirect coverage changes

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