Set frozen config as boolean

This is normalized to "true" in the config after running bin/bundle, so
rerunning script/configure_bundler resets this back to 1 (which is the
same, but we don't need to change this back and forth every time).

script/configure_bundler

@@ -24,7 +24,7 @@ end
 
 if rails_env != "development"
   config("path vendor/bundle")
-  config("frozen 1")
+  config("frozen true")
   config("disable_shared_gems true")
 end