fix rust 1.79.0 docs std crate indexing

lib/docs/filters/rust/clean_html.rb

@@ -19,6 +19,7 @@ module Docs
           css('.anchor').remove
 
           css('.main-heading > h1').each do |node|
+            node.at('button')&.remove
             node.parent.name = 'h1'
             node.parent.content = node.content
           end

lib/docs/filters/rust/entries.rb

@@ -9,6 +9,7 @@ module Docs
         elsif slug == 'error-index'
           'Compiler Errors'
         else
+          at_css('main h1').at_css('button')&.remove
           name = at_css('main h1').content.remove(/\A.+\s/).remove('⎘')
           mod = slug.split('/').first
           name.prepend("#{mod}::") unless name.start_with?(mod)