Fix some issues reported by lintian

Fix some issues reported by lintian

• Use secure URI in debian/watch. (debian-watch-uses-insecure-uri)
• Set Homepage field in Source rather than Binary package. (homepage-in-binary-package)
• Update standards version to 4.5.0, no changes needed. (out-of-date-standards-version)

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Build and test logs for this branch can be found at https://janitor.debian.net/lintian-fixes/pkg/milter-greylist/8758a428-2bcf-47f0-9f46-ece21ea16e57.

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/6c/2a9fe3a6adde1bf7aa64f6c0cff207432fcbad.debug

Files in first set of .debs but not in second

-rw-r--r--  root/root   /usr/lib/debug/.build-id/7e/c867d8dbfd30e060fc39fb0fc2b2cc36054625.debug

No differences were encountered between the control files of package **milter-greylist**

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

• Build-Ids: 7ec867d8dbfd30e060fc39fb0fc2b2cc36054625 6c2a9fe3a6adde1bf7aa64f6c0cff207432fcbad

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