Fix minor typos

```
codespell **/*.rb **/*.md -L initalize,unvalid
```

spec/authorization_spec.rb

@@ -166,7 +166,7 @@
       expect(controller.policy_scope(Post)).to eq :published
     end
 
-    it "allows policy scope class to be overriden" do
+    it "allows policy scope class to be overridden" do
       expect(controller.policy_scope(Post, policy_scope_class: PublicationPolicy::Scope)).to eq :published
     end
 

spec/spec_helper.rb

@@ -250,7 +250,7 @@ def self.all; end
 class ThreadPolicy < Struct.new(:user, :thread)
   class Scope < Struct.new(:user, :scope)
     def resolve
-      # deliberate wrong useage of the method
+      # deliberate wrong usage of the method
       scope.all(:unvalid, :parameters)
     end
   end