Merge branch 'bump-prometheus-version-to-fix-text-representation-problem' into 'master'

Update prometheus client gem

See merge request !12632

Gemfile.lock

@@ -599,8 +599,8 @@ GEM
     premailer-rails (1.9.7)
       actionmailer (>= 3, < 6)
       premailer (~> 1.7, >= 1.7.9)
-    prometheus-client-mmap (0.7.0.beta7)
-      mmap2 (~> 2.2.6)
+    prometheus-client-mmap (0.7.0.beta8)
+      mmap2 (~> 2.2, >= 2.2.7)
     pry (0.10.4)
       coderay (~> 1.1.0)
       method_source (~> 0.8.1)