Improve var naming, thanks Gaetan

spec/services/alert_spec.rb

@@ -43,10 +43,10 @@ RSpec.describe Alert do
 
   it "adds context given as keyword argument" do
     expect_any_instance_of(Bugsnag::Report).to receive(:add_metadata).with(
-      :data, { data: "ABC123" }
+      :thing, { data: "ABC123" }
     )
 
-    Alert.raise("hey", data: "ABC123")
+    Alert.raise("hey", thing: "ABC123")
   end
 
   it "adds simple values as context" do