Remove multi-line suggestions feature flag

That's a straightforward feature flag code removal for 11.10

lib/banzai/filter/suggestion_filter.rb

@@ -6,15 +6,11 @@ module Banzai
     class SuggestionFilter < HTML::Pipeline::Filter
       # Class used for tagging elements that should be rendered
       TAG_CLASS = 'js-render-suggestion'.freeze
-      SUGGESTION_REGEX = Gitlab::Diff::SuggestionsParser::SUGGESTION_CONTEXT
 
       def call
         return doc unless suggestions_filter_enabled?
 
         doc.search('pre.suggestion > code').each do |node|
-          # TODO: Remove once multi-line suggestions FF get removed (#59178).
-          remove_multi_line_params(node.parent)
-
           node.add_class(TAG_CLASS)
         end
 
@@ -30,14 +26,6 @@ module Banzai
       def project
         context[:project]
       end
-
-      def remove_multi_line_params(node)
-        return if Feature.enabled?(:multi_line_suggestions, project)
-
-        if node[SyntaxHighlightFilter::LANG_PARAMS_ATTR]&.match?(SUGGESTION_REGEX)
-          node.remove_attribute(SyntaxHighlightFilter::LANG_PARAMS_ATTR)
-        end
-      end
     end
   end
 end

spec/lib/banzai/filter/suggestion_filter_spec.rb

@@ -28,30 +28,11 @@ describe Banzai::Filter::SuggestionFilter do
     let(:data_attr) { Banzai::Filter::SyntaxHighlightFilter::LANG_PARAMS_ATTR }
     let(:input) { %(<pre class="code highlight js-syntax-highlight suggestion" #{data_attr}="-3+2"><code>foo\n</code></pre>) }
 
-    context 'feature disabled' do
-      before do
-        stub_feature_flags(multi_line_suggestions: false)
-      end
+    it 'element has correct data-lang-params' do
+      doc = filter(input, default_context)
+      pre = doc.css('pre').first
 
-      it 'removes data-lang-params if it matches a multi-line suggestion param' do
-        doc = filter(input, default_context)
-        pre = doc.css('pre').first
-
-        expect(pre[data_attr]).to be_nil
-      end
-    end
-
-    context 'feature enabled' do
-      before do
-        stub_feature_flags(multi_line_suggestions: true)
-      end
-
-      it 'keeps data-lang-params' do
-        doc = filter(input, default_context)
-        pre = doc.css('pre').first
-
-        expect(pre[data_attr]).to eq('-3+2')
-      end
+      expect(pre[data_attr]).to eq('-3+2')
     end
   end
 end