Add strict parameter to remove() TaggableManager.remove() method (fixes #928)

[Dzhud]

Summary

Fixes #928

This PR adds an optional strict parameter to the TaggableManager.remove() method, allowing users to opt-in to receiving an error when attempting to remove tags that are not associated with the object.

Changes

managers.py: Added strict=False parameter to remove() method. When strict=True, raises ValueError listing any tags not found on the object.
tests.py: Added 4 test cases covering the new functionality.
CHANGELOG.rst: Added entry for the new feature.
api.rst: Updated documentation with the new parameter.

Behaviour

# Default behavior (backwards compatible) - silently ignores missing tags
apple.tags.add("red", "green")
apple.tags.remove("blue")  # No error, nothing happens

# Strict mode - raises ValueError for missing tags
apple.tags.remove("blue", strict=True)  
# ValueError: The following tags are not associated with this object: blue