Update minimum version of ruby to 2.7

debian/control

@@ -20,7 +20,8 @@ Architecture: all
 XB-Ruby-Versions: ${ruby:Versions}
 Depends: ${shlibs:Depends}, ${misc:Depends},
  gitlab-common (>= 13.0.0~),
- ruby (>= 1:2.5~),
+ ruby (>= 1:2.7~),
+   rubygems-integration (>= 1.17.1~),
  lsb-base (>= 3.0-6),
  rake (>= 12.3.0~),
  bundler (>= 1.17.3~),
@@ -418,7 +419,7 @@ Depends: ${shlibs:Depends}, ${misc:Depends},
  puma
 Recommends: certbot,
  gitaly (>= 13.1~)
-Conflicts: libruby2.3
+Conflicts: libruby2.5
 Description: git powered software platform to collaborate on code (non-omnibus)
  gitlab provides web based interface to host source code and track issues.
  It allows anyone for fork a repository and send merge requests. Code review