Chore: Bump sqlglot-mypy to 1.20

[VaggelisD]

Mypy released 1.20 which includes our mypyc fixes but dropped Python 3.9.

This PR changes the following:

• setup.py: Use vanilla mypy for linting instead of sqlglot-mypy
• sqlglotc/pyproject.toml: Bump sqlglot-mypy to 1.20 and require Python >= 3.10
• package-publish.yml: Remove cp39 from mypyc wheel build matrix
• package-test.yml: Skip testc on 3.9 (run make style test instead of make check)

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Mypy 1.20 changelog

[github-actions]

SQLGlot Integration Test Results

Comparing:

• this branch (sqlglot:vaggelisd/bump_sqlglot_mypy, sqlglot version: vaggelisd/bump_sqlglot_mypy)
• baseline (main, sqlglot version: 0.0.1.dev1)

By Dialect

dialect	main	sqlglot:vaggelisd/bump_sqlglot_mypy	transitions	links
bigquery -> bigquery	23872/23877 passed (100.0%)	21252/21252 passed (100.0%)	No change	full result / delta
bigquery -> duckdb	2102/2624 passed (80.1%)	0/0 passed (0.0%)	No change	full result / delta
snowflake -> duckdb	1512/2674 passed (56.5%)	1512/2674 passed (56.5%)	No change	full result / delta
snowflake -> snowflake	65910/65910 passed (100.0%)	65910/65910 passed (100.0%)	No change	full result / delta
databricks -> databricks	1364/1364 passed (100.0%)	1364/1364 passed (100.0%)	No change	full result / delta
postgres -> postgres	6040/6040 passed (100.0%)	6040/6040 passed (100.0%)	No change	full result / delta
redshift -> redshift	7059/7059 passed (100.0%)	7059/7059 passed (100.0%)	No change	full result / delta

Overall

main: 109548 total, 107859 passed (pass rate: 98.5%), sqlglot version: 0.0.1.dev1

sqlglot:vaggelisd/bump_sqlglot_mypy: 108302 total, 107140 passed (pass rate: 98.9%), sqlglot version: vaggelisd/bump_sqlglot_mypy

Transitions:
No change

✅ 7 test(s) passed

[georgesittas]

A couple of questions to make sure we don't break the developer experience with these changes, LGTM otherwise.