fix: avoid duplicated completions names

lib/ruby_lsp/listeners/completion.rb

@@ -311,7 +311,7 @@ def handle_global_variable_completion(name, location)
 
         range = range_from_location(location)
 
-        candidates.flatten.each do |entry|
+        candidates.flatten.uniq(&:name).each do |entry|
           entry_name = entry.name
 
           @response_builder << Interface::CompletionItem.new(

test/requests/completion_test.rb

@@ -1065,6 +1065,28 @@ def test_completion_for_global_variables
     end
   end
 
+  def test_completion_for_global_variables_show_only_uniq_entries
+    source = <<~RUBY
+      $qar &&= 1
+      $qar += 1
+      $qar ||= 1
+      $q
+    RUBY
+
+    with_server(source) do |server, uri|
+      index = server.instance_variable_get(:@global_state).index
+      RubyIndexer::RBSIndexer.new(index).index_ruby_core
+
+      server.process_message(id: 1, method: "textDocument/completion", params: {
+        textDocument: { uri: uri },
+        position: { line: 3, character: 2 },
+      })
+
+      result = server.pop_response.response
+      assert_equal(["$qar"], result.map(&:label))
+    end
+  end
+
   def test_completion_for_instance_variables
     source = +<<~RUBY
       class Foo