[rubygems/rubygems] Explicitly set `allow_cached` to false when setting local mode

https://github.com/rubygems/rubygems/commit/1b8139e9d3

lib/bundler/source/rubygems.rb

@@ -29,6 +29,7 @@ module Bundler
       def local_only!
         @specs = nil
         @allow_local = true
+        @allow_cached = false
         @allow_remote = false
       end