[rubygems/rubygems] Remove unnecessary verification

`DSL#to_definition` already verifies this.

c596f0af83

lib/bundler/inline.rb

@@ -46,7 +46,6 @@ def gemfile(install = false, options = {}, &gemfile)
     Bundler::Plugin.gemfile_install(&gemfile) if Bundler.feature_flag.plugins?
     builder = Bundler::Dsl.new
     builder.instance_eval(&gemfile)
-    builder.check_primary_source_safety
 
     Bundler.settings.temporary(deployment: false, frozen: false) do
       definition = builder.to_definition(nil, true)