Fix some issues reported by lintian

Fix some issues reported by lintian

• Update lintian override info format in d/source/lintian-overrides on line 3-4. (mismatched-override)
• Bump debhelper from old 11 to 13. (package-uses-old-debhelper-compat-version)
• Set upstream metadata fields: Repository-Browse. (upstream-metadata-file-is-missing)
• Update standards version to 4.6.2, no changes needed. (out-of-date-standards-version)

These changes have no impact on the binary debdiff.

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Build and test logs for this branch can be found at https://janitor.debian.net/run/48d3743d-96e4-4dee-888e-2cedb32e3667.