Update Gitaly Gem to v13.9.0-rc1

In order to get hold of the new "timestamp" field added to a subset of
Gitaly RPCs, this commit updates the Gitaly Gem to v13.9.0-rc1.

Gemfile

@@ -464,7 +464,7 @@ group :ed25519 do
 end
 
 # Gitaly GRPC protocol definitions
-gem 'gitaly', '~> 13.8.0.pre.rc3'
+gem 'gitaly', '~> 13.9.0.pre.rc1'
 
 gem 'grpc', '~> 1.30.2'
 

Gemfile.lock

@@ -420,7 +420,7 @@ GEM
       rails (>= 3.2.0)
     git (1.7.0)
       rchardet (~> 1.8)
-    gitaly (13.8.0.pre.rc3)
+    gitaly (13.9.0.pre.rc1)
       grpc (~> 1.0)
     github-markup (1.7.0)
     gitlab-chronic (0.10.5)
@@ -1368,7 +1368,7 @@ DEPENDENCIES
   gettext (~> 3.3)
   gettext_i18n_rails (~> 1.8.0)
   gettext_i18n_rails_js (~> 1.3)
-  gitaly (~> 13.8.0.pre.rc3)
+  gitaly (~> 13.9.0.pre.rc1)
   github-markup (~> 1.7.0)
   gitlab-chronic (~> 0.10.5)
   gitlab-experiment (~> 0.4.9)