git-bz: use callPackage and canonical package name

Don't add a compatibility alias as this package was/is marked as
being broken anyway.

pkgs/applications/version-management/git-and-tools/default.nix

···
 rec {
 
   # support for bugzilla
-  gitBz = import ./git-bz {
-    inherit fetchgit stdenv makeWrapper python asciidoc xmlto # docbook2x docbook_xsl docbook_xml_dtd_45 libxslt
-      ;
-    inherit (pythonPackages) pysqlite;
-  };
+  git-bz = callPackage ./git-bz { };
 
   git = appendToName "minimal" gitBase;