upgrade github-linguist from 4.x to 7.x

Author: maedana

lib/qiita/markdown/filters/code_block.rb

@@ -86,7 +86,7 @@ def has_only_filename?
           end
 
           def linguist_language
-            @linguist_language ||= Linguist::Language.find_by_filename(filename).first
+            @linguist_language ||= Linguist::Language.find_by_extension(filename).first
           end
 
           def sections

qiita-markdown.gemspec

@@ -19,7 +19,7 @@ Gem::Specification.new do |spec|
 
   spec.add_dependency "addressable"
   spec.add_dependency "gemoji"
-  spec.add_dependency "github-linguist", "~> 4.0"
+  spec.add_dependency "github-linguist", "~> 7.0"
   spec.add_dependency "html-pipeline", "~> 2.0"
   spec.add_dependency "mem"
   spec.add_dependency "qiita_marker", "~> 0.23.9"