Fix some issues reported by lintian

Fix some issues reported by lintian

• Trim trailing whitespace. (trailing-whitespace)
• Use secure URI in Homepage field. (homepage-field-uses-insecure-uri)
• Set upstream metadata fields: Bug-Database, Contact, Name, Repository-Browse. (upstream-metadata-file-is-missing)
• Update standards version to 4.6.0, no changes needed. (out-of-date-standards-version)
• Trim trailing whitespace. (trailing-whitespace)
• Use secure URI in Homepage field. (homepage-field-uses-insecure-uri)
• Set upstream metadata fields: Contact, Name, Repository-Browse. (upstream-metadata-file-is-missing)
• 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 (out-of-date-standards-version)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/pitivi/0be3f088-920d-417a-a589-d0adb7231c5b.

Debdiff

These changes affect the binary packages:

[The following lists of changes regard files as different if they have different names, permissions or owners.]

Files in second set of .debs but not in first

-rw-r--r--  root/root   /usr/lib/debug/.build-id/93/50c6295f3a9b45a331648eac54e4ac4e0fe48f.debug

Files in first set of .debs but not in second

-rw-r--r--  root/root   /usr/lib/debug/.build-id/5c/7911c3948aa6b10c08d73ada40d0d6adb10c5f.debug

Control files of package pitivi: lines which differ (wdiff format)

• Homepage: [-http​://www.pitivi.org-] {+https​://www.pitivi.org+}

Control files of package pitivi-dbgsym: lines which differ (wdiff format)

• Build-Ids: 5c7911c3948aa6b10c08d73ada40d0d6adb10c5f 9350c6295f3a9b45a331648eac54e4ac4e0fe48f

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