deprecations isort and flake8 fix

[martynaut]

Weekly GAM scan + linter fixes — 2026-06-10

Dependency updates (requirements.txt)

• googleads>=42.0.0 → >=49.0.0 — v42 only supports SOAP API versions that are
  already sunset (v202405 was retired May 2025). v49 supports the four
  currently-active versions: v202505, v202508, v202511, v202602.
• pandas>=0.24.0 → >=2.0.0 — aligns the floor with the actual working minimum
  given the DataFrame.append() fix below.

Bug fixes

• gam_api.py — replaced DataFrame.append() with pd.concat() in
  get_users_from_admanager and get_companies_from_admanager. DataFrame.append()
  was removed in pandas 2.0 (April 2023); both functions would raise
  AttributeError on any current pandas install.

Linter fixes (flake8 + isort)

• replaced all type(x) == T / type(x) != T comparisons with
  isinstance() across gam_api.py, bigquery_api.py, athena_api_helpers.py,
  moat_api_helpers.py, neo4j_api.py, s3_connection_api.py
• removed unused permission = assignments in google_drive_api.py
  (return value of permissions().create().execute() was never read)
• fixed blank line counts in gam_api.py and
  google_drive_helpers.py
• stripped trailing whitespace from google_drive_api.py and
  google_drive_helpers.py
• isort — corrected import ordering (stdlib before third-party before local)
  and formatting in mysql.py, mysql_helpers.py, athena_api.py, qubole_api.py,
  bigquery_api.py, neo4j_api.py, google_drive_helpers.py