bump ruby version (as specified in github-pages v209)

fmichonneau · fmichonneau · commit 462be1ec5a97 · 2020-10-28T14:46:05.000+01:00
diff --git a/Gemfile b/Gemfile
@@ -5,6 +5,6 @@ source 'https://rubygems.org'
 git_source(:github) {|repo_name| "https://github.com/#{repo_name}" }
 
 # Synchronize with https://pages.github.com/versions
-ruby '>=2.5.8'
+ruby '>=2.7.1'
 
 gem 'github-pages', group: :jekyll_plugins
