remove unused variable

guides/rails_guides/markdown/renderer.rb

@@ -65,7 +65,7 @@ def convert_notes(body)
           # if a bulleted list follows the first item is not rendered
           # as a list item, but as a paragraph starting with a plain
           # asterisk.
-          body.gsub(/^(TIP|IMPORTANT|CAUTION|WARNING|NOTE|INFO|TODO)[.:](.*?)(\n(?=\n)|\Z)/m) do |m|
+          body.gsub(/^(TIP|IMPORTANT|CAUTION|WARNING|NOTE|INFO|TODO)[.:](.*?)(\n(?=\n)|\Z)/m) do
             css_class = case $1
                         when 'CAUTION', 'IMPORTANT'
                           'warning'