Fix some issues reported by lintian

Fix some issues reported by lintian

• Update lintian override info to new format: (mismatched-override)
• Trim trailing whitespace. (trailing-whitespace)
• Bump debhelper from old 12 to 13. (package-uses-old-debhelper-compat-version)
• Update renamed lintian tag names in lintian overrides. (renamed-tag)
• Set upstream metadata fields: Bug-Database, Bug-Submit, Repository-Browse. (upstream-metadata-file-is-missing, upstream-metadata-missing-bug-tracking)
• Update standards version to 4.6.1, no changes needed. (out-of-date-standards-version)

This merge proposal was created by the Janitor bot, and it will automatically rebase or close this proposal as appropriate when the target branch changes. Any comments you leave here will be read by the Janitor's maintainers.

Build and test logs for this branch can be found at https://janitor.debian.net/lintian-fixes/pkg/opa-ff/a1b576af-82d8-479f-883b-cdddfa57388c.

These changes affect the binary packages; see the debdiff

You can also view the diffoscope diff (unfiltered).