ci: add missing top level contents permission

[vdusek]

Description

Two workflows in this repo were missing a top-level permissions: contents: read block:

• .github/workflows/manual_release_docs.yaml
• .github/workflows/on_issue.yaml

The other workflows here, as well as the equivalents in apify-sdk-python and crawlee-python, all set this default at the file level. This applies the principle of least privilege: jobs that need to escalate (e.g. contents: write, pages: write, issues: write) still do so via job-level overrides.

Changes

• Add permissions: contents: read at the top level of both workflow files.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.50%. Comparing base (94d5bf4) to head (a1a6f26).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #779      +/-   ##
==========================================
- Coverage   97.56%   97.50%   -0.07%     
==========================================
  Files          47       47              
  Lines        4725     4725              
==========================================
- Hits         4610     4607       -3     
- Misses        115      118       +3     

Flag	Coverage Δ
integration	95.28% <ø> (-0.26%)	⬇️
unit	82.11% <ø> (ø)

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