Use latest hatchet instead of git branch (#558)

Gemfile

 source "https://rubygems.org"
 
-gem 'heroku_hatchet', :git => 'https://github.com/heroku/hatchet.git', :branch => 'support-local-directories-for-fixtures'
+gem 'heroku_hatchet'
 gem 'rspec-retry'
 gem 'rspec-expectations'
 gem 'sem_version'

Gemfile.lock

-GIT
-  remote: https://github.com/heroku/hatchet.git
-  revision: 4ea40af89e00d49dd21f9695ce99f21219a0455b
-  branch: support-local-directories-for-fixtures
-  specs:
-    heroku_hatchet (4.0.4)
-      excon (~> 0)
-      minitest-retry (~> 0.1.9)
-      platform-api (~> 2)
-      repl_runner (~> 0.0.3)
-      rrrretry (~> 1)
-      thor (~> 0)
-      threaded (~> 0)
-
 GEM
   remote: https://rubygems.org/
   specs:
@@ -29,6 +15,14 @@ GEM
       excon
       moneta
       multi_json (>= 1.9.2)
+    heroku_hatchet (4.0.5)
+      excon (~> 0)
+      minitest-retry (~> 0.1.9)
+      platform-api (~> 2)
+      repl_runner (~> 0.0.3)
+      rrrretry (~> 1)
+      thor (~> 0)
+      threaded (~> 0)
     i18n (1.1.0)
       concurrent-ruby (~> 1.0)
     minitest (5.11.3)
@@ -65,7 +59,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  heroku_hatchet!
+  heroku_hatchet
   parallel_tests
   rake
   rspec-expectations