Fix some issues reported by lintian

Fix some issues reported by lintian

• Use versioned copyright format URI. (unversioned-copyright-format-uri)
• Bump debhelper from old 11 to 12. (package-uses-old-debhelper-compat-version)
• Set debhelper-compat version in Build-Depends. (uses-debhelper-compat-file)

This merge proposal was created automatically by the Janitor bot.

You can follow up to this merge proposal as you normally would.

Build and test logs for this branch can be found at https://janitor.debian.net/lintian-fixes/pkg/gemdropx/0e2c0a2d-9671-4041-8e2f-397d44db86fe.

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/d2/377ca6b3d7eecc3ef536a45d572f2629430007.debug

Files in first set of .debs but not in second

-rw-r--r--  root/root   /usr/lib/debug/.build-id/95/d94574ad12e723f85ed62c15f84e6681424ac8.debug

No differences were encountered between the control files of package **gemdropx**

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

• Build-Ids: 95d94574ad12e723f85ed62c15f84e6681424ac8 d2377ca6b3d7eecc3ef536a45d572f2629430007

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