Merge pull request gliderlabs#1053 from gliderlabs/dependabot/bundler/buildpacks/buildpack-multi/tests/multi/sinatra-and-rack-3.1.0

chore(deps): bump sinatra and rack in /buildpacks/buildpack-multi/tests/multi

Author: josegonzalez

buildpacks/buildpack-multi/tests/multi/Gemfile.lock

@@ -1,9 +1,18 @@
 GEM
   remote: http://rubygems.org/
   specs:
-    rack (3.0.8)
-    sinatra (1.0)
-      rack (>= 1.0)
+    mustermann (3.0.0)
+      ruby2_keywords (~> 0.0.1)
+    rack (2.2.8)
+    rack-protection (3.1.0)
+      rack (~> 2.2, >= 2.2.4)
+    ruby2_keywords (0.0.5)
+    sinatra (3.1.0)
+      mustermann (~> 3.0)
+      rack (~> 2.2, >= 2.2.4)
+      rack-protection (= 3.1.0)
+      tilt (~> 2.0)
+    tilt (2.3.0)
 
 PLATFORMS
   ruby