DEV: Fix another report flaky (#28868)

Followup 0323b366f3023843468d1024135bbb1c7c6f0483

This was happening because another spec was adding a
report using the plugin API, but there was nothing
resetting that, so later in the reports controller
when we did Report.singleton_methods, we ended up
with another report with no translation, causing another
error.

spec/lib/plugin/instance_spec.rb

@@ -358,6 +358,8 @@ TEXT
   end
 
   describe "#add_report" do
+    after { Report.remove_report("readers") }
+
     it "adds a report" do
       plugin = Plugin::Instance.new nil, "/tmp/test.rb"
       plugin.add_report("readers") {}