[bundler/bundler] Change the refresh spec to not use stubs_for

We plan to incrementally populate this array in rubygems, so that will
break the test because the first time `find_by_name("rack")` is called
will make the `rack` gem available in the array.

We can test the same thing using some other way, which is more
appropriate anyways, because `Bundler.rubygems.find_name` is only used
inside `bundler` to look for the `bundler` gem itself whereas
`Bundler.rubygems.all_specs` is used in more places.

https://github.com/bundler/bundler/commit/49c519ef47

spec/bundler/runtime/setup_spec.rb

@@ -854,12 +854,12 @@ end
     G
 
     run <<-R
-      puts Bundler.rubygems.find_name("rack").inspect
+      puts Bundler.rubygems.all_specs.map(&:name)
       Gem.refresh
-      puts Bundler.rubygems.find_name("rack").inspect
+      puts Bundler.rubygems.all_specs.map(&:name)
     R
 
-    expect(out).to eq("[]\n[]")
+    expect(out).to eq("activesupport\nbundler\nactivesupport\nbundler")
   end
 
   describe "when a vendored gem specification uses the :path option" do