Use version dependant library for completion test

Author: hsbt

test/irb/test_completion.rb

@@ -124,8 +124,8 @@ def object.to_s; raise; end
       end
 
       def test_complete_require_library_name_first
-        candidates = IRB::RegexpCompletor.new.completion_candidates("require ", "'csv", "", bind: binding)
-        assert_equal "'csv", candidates.first
+        candidates = IRB::RegexpCompletor.new.completion_candidates("require ", "'coverage", "", bind: binding)
+        assert_equal "'coverage", candidates.first
       end
 
       def test_complete_require_relative