fix: correctly parse PUSHER_USE_SSL environment variable (#6582)

[ChickenisLegit]

Closes #6582.

This PR fixes a bug where setting PUSHER_USE_SSL=false in Docker Compose or other environments would evaluate to True.
This occurred because os.environ.get returns a string (e.g. "false"), which evaluated to True since any non-empty string in Python evaluates to True when checked against False (e.g. ssl=False if os.environ.get("PUSHER_USE_SSL", False) is False else True).

Changes

• Updated PUSHER_USE_SSL parsing to properly handle string booleans ("false", "0", "true", "1", "yes", "on").
• Defaults to "false" if the environment variable is not present, matching the existing fallback logic.

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[ChickenisLegit]

I have read the CLA Document and I hereby sign the CLA

[github-actions]

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