contrib: Remove C-style comments from Python files

These Python scripts have "*/" at the end of the license header comment
blocks, presumably copy&pasted from C files.

contrib/ChangeLog:

	* analyze_brprob.py: Remove stray text at end of comment.
	* analyze_brprob_spec.py: Likewise.
	* check-params-in-docs.py: Likewise.
	* check_GNU_style.py: Likewise.
	* check_GNU_style_lib.py: Likewise.
	* filter-clang-warnings.py: Likewise.
	* gcc-changelog/git_check_commit.py: Likewise.
	* gcc-changelog/git_commit.py: Likewise.
	* gcc-changelog/git_email.py: Likewise.
	* gcc-changelog/git_repository.py: Likewise.
	* gcc-changelog/git_update_version.py: Likewise.
	* gcc-changelog/test_email.py: Likewise.
	* gen_autofdo_event.py: Likewise.
	* mark_spam.py: Likewise.
	* unicode/gen-box-drawing-chars.py: Likewise.
	* unicode/gen-combining-chars.py: Likewise.
	* unicode/gen-printable-chars.py: Likewise.
	* unicode/gen_wcwidth.py: Likewise.