Update bug links from Bugzilla to GitLab issues (!11)

- Bugzilla has disabled reporting of new bugs.
- Existing Bugzilla bug reports permit new comments only.
- New bugs are to be created on GitLab issues.

Reference:
[GitLab] IMPORTANT: Mass migration plan
https://mail.gnome.org/archives/desktop-devel-list/2018-March/msg00023.html

Closes !11 - Update bugzilla references

configure.ac

@@ -1,4 +1,4 @@
-AC_INIT([gparted],[0.32.0-git],[https://bugzilla.gnome.org/enter_bug.cgi?product=gparted])
+AC_INIT([gparted],[0.32.0-git],[https://gitlab.gnome.org/GNOME/gparted/issues])
 AC_PREREQ([2.50])
 
 AC_CONFIG_SRCDIR([src/main.cc])

gparted.doap

@@ -16,7 +16,7 @@
   <shortdesc xml:lang="en">GNOME Partition Editor for manipulating disk partitions</shortdesc>
   <homepage rdf:resource="https://gparted.org" />
   <download-page rdf:resource="https://gparted.org/download.php" />
-  <bug-database rdf:resource="https://bugzilla.gnome.org/browse.cgi?product=gparted" />
+  <bug-database rdf:resource="https://gitlab.gnome.org/GNOME/gparted/issues" />
 
   <maintainer>
     <foaf:Person>