Update guides/upgrading/v0.14.md

Co-authored-by: Copilot <[email protected]>

Author: Flo0807

guides/upgrading/v0.14.md

@@ -91,11 +91,11 @@ Make sure to update your custom fields accordingly. The `readonly` value will be
 ```elixir
 @impl Backpex.Field
 def render_form(%{readonly: true} = assigns) do
-# render readonly field
+# Render readonly field
 end
 
 def render_form(%{readonly: false} = assigns) do
-# render editable field
+# Render editable field
 end
 ```