fix(bitbucket): normalize issue comment deleted flag

[KatalKavya96]

Summary

• Normalizes Bitbucket Cloud issue comment deleted values through _bool_or_none() for consistency with existing PR discussion comment handling.
• Adds test coverage for boolean deleted issue comments.
• Follows up on the optional reviewer nit from feat(bitbucket): add read-only cloud issue comments fetch #864.

Type of change

• Python package (tools/*/ with pyproject.toml)

Test plan

• PYTHONPATH=src uv run --group dev pytest tests/test_bitbucket.py -q -k "issue_comments or issue_comment"
• PYTHONPATH=src uv run --group dev pytest tests/test_bitbucket.py -q
• uv run --group dev ruff check src tests --fix
• uv run --group dev ruff format src tests
• uv run --group dev mypy src tests
• git diff --check

Linked issues

Refs #606

[KatalKavya96]

Hi @potiuk, I opened a small follow-up from your #864 nit.

This normalizes Cloud issue comment deleted through _bool_or_none() for consistency with PR discussion comments and adds a small test.

Targeted pytest, full Bitbucket pytest, ruff, mypy, and git diff --check are passing.

[KatalKavya96]

Thanks for the review and approval @potiuk. Could you please merge this one when you get a chance, so I can move ahead with the next Bitbucket follow-up for #606?