Start filtering ::PP::ObjectMixin again

I have no idea why we've started seeing these creep into our RBI files
for some tests on CI, but I can't reproduce it locally, so I'm going to
start filtering these out again to make our CI green.

Author: paracycle

spec/tapioca/gem/pipeline_spec.rb

@@ -337,7 +337,7 @@ def log; end
         end
       RBI
 
-      compiled = compile
+      compiled = compile.gsub(/^\s+include ::PP::ObjectMixin\s/, "")
 
       assert_includes(compiled, basic_object_output)
       assert_includes(compiled, object_output)
@@ -373,7 +373,9 @@ class Object < ::BasicObject
         end
       RBI
 
-      assert_includes(compile, output)
+      compiled = compile.gsub(/^\s+include ::PP::ObjectMixin\s/, "")
+
+      assert_includes(compiled, output)
     end
 
     it "compiles mixins in the correct order" do