Update gitlab-experiment to 0.5.1

- This includes an important bug fix.

Gemfile

@@ -488,7 +488,7 @@ gem 'flipper', '~> 0.17.1'
 gem 'flipper-active_record', '~> 0.17.1'
 gem 'flipper-active_support_cache_store', '~> 0.17.1'
 gem 'unleash', '~> 0.1.5'
-gem 'gitlab-experiment', '~> 0.5.0'
+gem 'gitlab-experiment', '~> 0.5.1'
 
 # Structured logging
 gem 'lograge', '~> 0.5'

Gemfile.lock

@@ -438,9 +438,9 @@ GEM
       numerizer (~> 0.2)
     gitlab-dangerfiles (0.8.0)
       danger
-    gitlab-experiment (0.5.0)
+    gitlab-experiment (0.5.1)
       activesupport (>= 3.0)
-      scientist (~> 1.5, >= 1.5.0)
+      scientist (~> 1.6, >= 1.6.0)
     gitlab-fog-azure-rm (1.0.1)
       azure-storage-blob (~> 2.0)
       azure-storage-common (~> 2.0)
@@ -1422,7 +1422,7 @@ DEPENDENCIES
   github-markup (~> 1.7.0)
   gitlab-chronic (~> 0.10.5)
   gitlab-dangerfiles (~> 0.8.0)
-  gitlab-experiment (~> 0.5.0)
+  gitlab-experiment (~> 0.5.1)
   gitlab-fog-azure-rm (~> 1.0.1)
   gitlab-fog-google (~> 1.13)
   gitlab-labkit (~> 0.16.1)