Use gitaly-proto 0.31.0

Gemfile

@@ -401,7 +401,7 @@ group :ed25519 do
 end
 # Gitaly GRPC client
-gem 'gitaly', '~> 0.30.0'
+gem 'gitaly-proto', '~> 0.31.0', require: 'gitaly'
 gem 'toml-rb', '~> 0.3.15', require: false

Gemfile.lock

@@ -275,7 +275,7 @@ GEM
       po_to_json (>= 1.0.0)
       rails (>= 3.2.0)
     gherkin-ruby (0.3.2)
-    gitaly (0.30.0)
+    gitaly-proto (0.31.0)
       google-protobuf (~> 3.1)
       grpc (~> 1.0)
     github-linguist (4.7.6)
@@ -1019,7 +1019,7 @@ DEPENDENCIES
   gettext (~> 3.2.2)
   gettext_i18n_rails (~> 1.8.0)
   gettext_i18n_rails_js (~> 1.2.0)
-  gitaly (~> 0.30.0)
+  gitaly-proto (~> 0.31.0)
   github-linguist (~> 4.7.0)
   gitlab-flowdock-git-hook (~> 1.0.1)
   gitlab-markup (~> 1.5.1)