docs: fix punctuation in Short and flag descriptions
Description
Fixes missing trailing periods and incorrect capitalization in Short
field and flag description strings across multiple Go source files.
These strings are the source of truth for the generated CLI
documentation (make gen-docs). The changes bring them into
conformance with the GitLab CLI style guide, which requires:
Related issues
Documentation
If this MR adds or updates CLI command documentation, follow the conventions in the
GitLab CLI (glab) documentation style guide,
run make gen-docs, and commit the updated files in docs/source/.