[rubygems/rubygems] Remove reference to validate_rust_builder_rubygems_version

Signed-off-by: Samuel Giddins <segiddins@segiddins.me>

ruby/rubygems@f8baf13ab0

Author: segiddins

lib/bundler/cli/gem.rb

@@ -31,7 +31,6 @@ def initialize(options, gem_name, thor)
       @extension = options[:ext]
 
       validate_ext_name if @extension
-      validate_rust_builder_rubygems_version if @extension == "rust"
     end
 
     def run