Update RUBY_PLATFORM conditional to Ruby 3.1

Differential Revision: D65979906

fbshipit-source-id: bc7e0e3856ea7006213ccf212a40b59086aad148

Author: Billy Barrese

cookbooks/fb_helpers/libraries/fb_helpers.rb

@@ -558,7 +558,7 @@ def self.linux?
     end
 
     def self.windows?
-      RUBY_PLATFORM =~ /mswin|mingw32|windows/
+      RUBY_PLATFORM =~ /mswin|mingw|windows/
     end
 
     # mountpoint? determines if a path string represents a mountpoint