extend/pathname: import rmtree again.

The separate file is no longer required now that
https://github.com/sorbet/sorbet/pull/7895 was merged.

Library/.rubocop.yml

@@ -284,7 +284,6 @@ Sorbet/TrueSigil:
     - "/**/{Formula,Casks}/**/*.rb"
     - "**/{Formula,Casks}/**/*.rb"
     - "Homebrew/test/**/*.rb"
-    - "Homebrew/extend/pathname/rmtree.rb"
 
 # Require &&/|| instead of and/or
 Style/AndOr:

Library/Homebrew/.rubocop.yml

@@ -33,7 +33,6 @@ Style/Documentation:
     - extend/ENV/super.rb
     - extend/kernel.rb
     - extend/pathname.rb
-    - extend/pathname/rmtree.rb
     - formula.rb
     - formula_assertions.rb
     - formula_free_port.rb

Library/Homebrew/extend/pathname.rb

@@ -498,6 +498,21 @@ class Pathname
                  .encode(Encoding::UTF_8, invalid: :replace)
                  .split("\n")
   end
+
+  # Like regular `rmtree`, except it never ignores errors.
+  #
+  # This was the default behaviour in Ruby 3.1 and earlier.
+  #
+  # @api public
+  def rmtree(noop: nil, verbose: nil, secure: nil)
+    # Ideally we'd odeprecate this but probably can't given gems so let's
+    # create a RuboCop autocorrect instead soon.
+    # This is why monkeypatching is non-ideal (but right solution to get
+    # Ruby 3.3 over the line).
+    # odeprecated "rmtree", "FileUtils#rm_r"
+    FileUtils.rm_r(@path, noop:, verbose:, secure:)
+    nil
+  end
 end
 
 require "extend/os/pathname"
@@ -584,5 +599,3 @@ module ObserverPathnameExtension
     puts "uninfo #{self}" if ObserverPathnameExtension.verbose?
   end
 end
-
-require "extend/pathname/rmtree"

Library/Homebrew/extend/pathname/rmtree.rb

@@ -1,19 +0,0 @@
-# typed: false
-# frozen_string_literal: true
-
-class Pathname
-  # Like regular `rmtree`, except it never ignores errors.
-  #
-  # This was the default behaviour in Ruby 3.1 and earlier.
-  #
-  # @api public
-  def rmtree(noop: nil, verbose: nil, secure: nil)
-    # Ideally we'd odeprecate this but probably can't given gems so let's
-    # create a RuboCop autocorrect instead soon.
-    # This is why monkeypatching is non-ideal (but right solution to get
-    # Ruby 3.3 over the line).
-    # odeprecated "rmtree", "FileUtils#rm_r"
-    FileUtils.rm_r(@path, noop:, verbose:, secure:)
-    nil
-  end
-end