Remove unused directory assignment in documentation generator

[coderabbitai]

Summary

Remove the unused directory = path assignment from generate_documentation_on_path().

Rationale

The function now uses path directly for the skip-list check and for documentation generation, so the local directory variable is unused.

Affected area

• scripts/gen_doc.py
• generate_documentation_on_path()

Required changes

Delete the unused assignment while preserving the existing path.as_posix() check against DIRS_TO_SKIP.

Acceptance criteria

• generate_documentation_on_path() no longer assigns path to an unused local variable.
• The configured-directory skip behavior remains unchanged.

Backlinks

• Pull request: LCORE-3141: Ability to disable some directories #2191
• Review comment: LCORE-3141: Ability to disable some directories #2191 (comment)

Requested by: @tisnik