Fix SmartProperties docs to show module structure (#2331)

### Motivation
<!-- Explain why you are making this change. Include links to issues or describe the problem being solved, not the solution. -->

The `SmartProperties` compiler generates methods inside a
`SmartPropertiesGeneratedMethods` module that gets included in the
class, but the documentation example showed methods directly on
the class. This updates the docs to match the actual implementation,
consistent with how other compilers like `ActiveRecordColumns` work.

### Implementation
<!-- How did you implement your changes? Explain your solution, design decisions, things reviewers should watch out for. -->

Updated the doc to reflect the actual module structure.

### Tests
<!-- We hope you added tests as part of your changes, just state that you have. If you haven't, state why. -->
No tests were added as this is a documentation-only change

Author: allcre

lib/tapioca/dsl/compilers/smart_properties.rb

@@ -29,29 +29,33 @@ module Compilers
       # # post.rbi
       # # typed: true
       # class Post
-      #   sig { returns(T.nilable(::String)) }
-      #   def title; end
+      #   include SmartPropertiesGeneratedMethods
       #
-      #   sig { params(title: T.nilable(::String)).returns(T.nilable(::String)) }
-      #   def title=(title); end
+      #   module SmartPropertiesGeneratedMethods
+      #     sig { returns(T.nilable(::String)) }
+      #     def title; end
       #
-      #   sig { returns(::String) }
-      #   def description; end
+      #     sig { params(title: T.nilable(::String)).returns(T.nilable(::String)) }
+      #     def title=(title); end
       #
-      #   sig { params(description: ::String).returns(::String) }
-      #   def description=(description); end
+      #     sig { returns(::String) }
+      #     def description; end
       #
-      #   sig { returns(T.nilable(T::Boolean)) }
-      #   def published?; end
+      #     sig { params(description: ::String).returns(::String) }
+      #     def description=(description); end
       #
-      #   sig { params(published: T.nilable(T::Boolean)).returns(T.nilable(T::Boolean)) }
-      #   def published=(published); end
+      #     sig { returns(T.nilable(T::Boolean)) }
+      #     def published?; end
       #
-      #   sig { returns(T.nilable(T::Boolean)) }
-      #   def enabled; end
+      #     sig { params(published: T.nilable(T::Boolean)).returns(T.nilable(T::Boolean)) }
+      #     def published=(published); end
       #
-      #   sig { params(enabled: T.nilable(T::Boolean)).returns(T.nilable(T::Boolean)) }
-      #   def enabled=(enabled); end
+      #     sig { returns(T.nilable(T::Boolean)) }
+      #     def enabled; end
+      #
+      #     sig { params(enabled: T.nilable(T::Boolean)).returns(T.nilable(T::Boolean)) }
+      #     def enabled=(enabled); end
+      #   end
       # end
       # ~~~
       #: [ConstantType = singleton(::SmartProperties)]

manual/compiler_smartproperties.md

@@ -23,29 +23,33 @@ this compiler will produce the RBI file `post.rbi` with the following content:
 # post.rbi
 # typed: true
 class Post
-  sig { returns(T.nilable(::String)) }
-  def title; end
+  include SmartPropertiesGeneratedMethods
 
-  sig { params(title: T.nilable(::String)).returns(T.nilable(::String)) }
-  def title=(title); end
+  module SmartPropertiesGeneratedMethods
+    sig { returns(T.nilable(::String)) }
+    def title; end
 
-  sig { returns(::String) }
-  def description; end
+    sig { params(title: T.nilable(::String)).returns(T.nilable(::String)) }
+    def title=(title); end
 
-  sig { params(description: ::String).returns(::String) }
-  def description=(description); end
+    sig { returns(::String) }
+    def description; end
 
-  sig { returns(T.nilable(T::Boolean)) }
-  def published?; end
+    sig { params(description: ::String).returns(::String) }
+    def description=(description); end
 
-  sig { params(published: T.nilable(T::Boolean)).returns(T.nilable(T::Boolean)) }
-  def published=(published); end
+    sig { returns(T.nilable(T::Boolean)) }
+    def published?; end
 
-  sig { returns(T.nilable(T::Boolean)) }
-  def enabled; end
+    sig { params(published: T.nilable(T::Boolean)).returns(T.nilable(T::Boolean)) }
+    def published=(published); end
 
-  sig { params(enabled: T.nilable(T::Boolean)).returns(T.nilable(T::Boolean)) }
-  def enabled=(enabled); end
+    sig { returns(T.nilable(T::Boolean)) }
+    def enabled; end
+
+    sig { params(enabled: T.nilable(T::Boolean)).returns(T.nilable(T::Boolean)) }
+    def enabled=(enabled); end
+  end
 end
 ~~~
 : [ConstantType = singleton(::SmartProperties)]