Remove grpc and google-protobuf platform-specific version markers in Gemfile.lock

Closes gitlab-org/omnibus-gitlab#3128

Gemfile.lock

@@ -340,7 +340,7 @@ GEM
       mime-types (~> 3.0)
       representable (~> 3.0)
       retriable (>= 2.0, < 4.0)
-    google-protobuf (3.5.1.1-universal-darwin)
+    google-protobuf (3.5.1.1)
     googleapis-common-protos-types (1.0.1)
       google-protobuf (~> 3.0)
     googleauth (0.5.3)
@@ -369,7 +369,7 @@ GEM
       rake
     grape_logging (1.7.0)
       grape
-    grpc (1.8.3-universal-darwin)
+    grpc (1.8.3)
       google-protobuf (~> 3.1)
       googleapis-common-protos-types (~> 1.0.0)
       googleauth (>= 0.5.1, < 0.7)