Switch rails 4 to 5 in gitlab-ci

CI jobs will be triggered both with rails 4 and 5
to make sure we keep backward compatibility if it turns out
we have to switch back to rails 4.

Rails 4 jobs are not allowed to fail for now, these jobs will be
removed in a follow-up MR next cycle.

scripts/rails4-gemfile-lock-check

+#!/usr/bin/env bash
+
+echo -e "=> Checking if Gemfile.rails4.lock is up-to-date...\\n"
+
+cp Gemfile.rails4.lock Gemfile.rails4.lock.orig
+BUNDLE_GEMFILE=Gemfile.rails4 bundle install "$BUNDLE_INSTALL_FLAGS"
+diff -u Gemfile.rails4.lock.orig Gemfile.rails4.lock >/dev/null 2>&1
+
+if [ $? == 1 ]
+then
+  diff -u Gemfile.rails4.lock.orig Gemfile.rails4.lock
+
+  echo -e "\\n✖ ERROR: Gemfile.rails4.lock is not up-to-date!
+         Please run 'BUNDLE_GEMFILE=Gemfile.rails4 bundle install'\\n" >&2
+  exit 1
+fi
+
+echo "✔ Gemfile.rails4.lock is up-to-date"
+exit 0

scripts/rails5-gemfile-lock-check

-#!/usr/bin/env bash
-
-echo -e "=> Checking if Gemfile.rails5.lock is up-to-date...\\n"
-
-cp Gemfile.rails5.lock Gemfile.rails5.lock.orig
-BUNDLE_GEMFILE=Gemfile.rails5 bundle install "$BUNDLE_INSTALL_FLAGS"
-diff -u Gemfile.rails5.lock.orig Gemfile.rails5.lock >/dev/null 2>&1
-
-if [ $? == 1 ]
-then
-  diff -u Gemfile.rails5.lock.orig Gemfile.rails5.lock
-
-  echo -e "\\n✖ ERROR: Gemfile.rails5.lock is not up-to-date!
-         Please run 'BUNDLE_GEMFILE=Gemfile.rails5 bundle install'\\n" >&2
-  exit 1
-fi
-
-echo "✔ Gemfile.rails5.lock is up-to-date"
-exit 0