Fix flaky test case test_autocomplete_with_multiple_doc_namespaces (#786)

Author: hogelog

test/irb/yamatanooroti/test_rendering.rb

@@ -207,15 +207,13 @@ def test_autocomplete_with_multiple_doc_namespaces
     write_irbrc <<~'LINES'
       puts 'start IRB'
     LINES
-    start_terminal(4, 40, %W{ruby -I#{@pwd}/lib #{@pwd}/exe/irb}, startup_message: 'start IRB')
+    start_terminal(3, 50, %W{ruby -I#{@pwd}/lib #{@pwd}/exe/irb}, startup_message: 'start IRB')
     write("{}.__id_")
     write("\C-i")
     close
-    assert_screen(<<~EOC)
-      start IRB
-      irb(main):001> {}.__id__
-                      }.__id__
-    EOC
+    screen = result.join("\n").sub(/\n*\z/, "\n")
+    # This assertion passes whether showdoc dialog completed or not.
+    assert_match(/start\ IRB\nirb\(main\):001> {}\.__id__\n                }\.__id__(?:Press )?/, screen)
   end
 
   def test_autocomplete_with_showdoc_in_gaps_on_narrow_screen_right