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)
• Bump debhelper from old 10 to 13. (package-uses-old-debhelper-compat-version)
• Set debhelper-compat version in Build-Depends. (uses-debhelper-compat-file)
• Set upstream metadata fields: Bug-Database, Bug-Submit, Repository-Browse. (upstream-metadata-file-is-missing, upstream-metadata-missing-bug-tracking)

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/ocamlagrep/c0fa9522-f967-4c14-b1f6-73c053883d66.

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/59/b314fc5a47659136ff4eb1a2ab059838204f30.debug

Files in first set of .debs but not in second

-rw-r--r--  root/root   /usr/lib/debug/.build-id/a7/52d8d00ec2cdcf9dfb8d40b60d61537861ac14.debug

Control files of package libagrep-ocaml: lines which differ (wdiff format)

• Homepage: [-http​://forge.ocamlcore.org/projects/ocamlagrep/-] {+https​://forge.ocamlcore.org/projects/ocamlagrep/+}

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

• Build-Ids: a752d8d00ec2cdcf9dfb8d40b60d61537861ac14 59b314fc5a47659136ff4eb1a2ab059838204f30

Control files of package libagrep-ocaml-dev: lines which differ (wdiff format)

• Homepage: [-http​://forge.ocamlcore.org/projects/ocamlagrep/-] {+https​://forge.ocamlcore.org/projects/ocamlagrep/+}

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