ErrorHandler should cleanup the scope

Because ErrorHandler is called outside of context middlewares,
we don't clean the scope when an exception occurs. This makes sure
ErrorHandler can have the context data set by middlewares. However, this
also means that those states would be left uncleaned after the exception is captured.

This commit makes sure that the scope is cleaned up after the exception is captured.

sentry-sidekiq/lib/sentry/sidekiq/error_handler.rb

@@ -25,6 +25,8 @@ def call(ex, context)
           contexts: { sidekiq: context_filter.filtered },
           hint: { background: false }
         )
+      ensure
+        scope&.clear
       end
 
       private

sentry-sidekiq/spec/sentry/sidekiq_spec.rb

@@ -75,6 +75,7 @@
       expect(event["tags"]).to eq("queue" => "default", "jid" => "123123", "mood" => "sad")
       expect(event["transaction"]).to eq("Sidekiq/SadWorker")
       expect(event["breadcrumbs"]["values"][0]["message"]).to eq("I'm sad!")
+      expect(Sentry.get_current_scope.tags).to be_empty
     end
 
     it "cleans up context from failed jobs" do
@@ -86,6 +87,7 @@
 
       expect(event["tags"]).to eq("queue" => "default", "jid" => "123123", "mood" => "very sad")
       expect(event["breadcrumbs"]["values"][0]["message"]).to eq("I'm very sad!")
+      expect(Sentry.get_current_scope.tags).to be_empty
     end
   end