[rubygems/rubygems] Stop generating binstubs with support for RubyGems before 2.6.2

RubyGems generated binstubs still provide support for this ancient
version. This makes no sense since we prevent downgrades to such old
versions.

ruby/rubygems@089cdc3b77

Author: deivid-rodriguez

lib/rubygems/installer.rb

@@ -771,12 +771,7 @@ def app_script_text(bin_file_name)
   end
 end
 
-if Gem.respond_to?(:activate_bin_path)
 load Gem.activate_bin_path('#{spec.name}', '#{bin_file_name}', version)
-else
-gem #{spec.name.dump}, version
-load Gem.bin_path(#{spec.name.dump}, #{bin_file_name.dump}, version)
-end
 TEXT
   end
 

test/rubygems/test_gem_installer.rb

@@ -48,12 +48,7 @@ def test_app_script_text
   end
 end
 
-if Gem.respond_to?(:activate_bin_path)
 load Gem.activate_bin_path('a', 'executable', version)
-else
-gem "a", version
-load Gem.bin_path("a", "executable", version)
-end
       EOF
 
       wrapper = installer.app_script_text "executable"