Fix some issues reported by lintian

Fix some issues reported by lintian

• Bump debhelper from old 9 to 12. (package-uses-old-debhelper-compat-version)
• Set upstream metadata fields: Repository, Repository-Browse. (upstream-metadata-file-is-missing)
• Make "Files: *" paragraph the first in the copyright file. (global-files-wildcard-not-first-paragraph-in-dep5-copyright)

This merge proposal was created automatically by the Janitor bot.

You can follow up to this merge proposal as you normally would.

Build and test logs for this branch can be found at https://janitor.debian.net/lintian-fixes/pkg/python-termcolor/455120b3-290b-40e1-8d50-664b42854a01.

These changes have no impact on the binary debdiff.

You can also view the diffoscope diff (unfiltered).