Tweak shlex.quote tests based on picnixz's review

Add test to ensure string with single quote inside it (without which the
string wouldn't need quoting) is quoted even though `force=False`.

Author: jb2170

Lib/test/test_shlex.py

@@ -348,6 +348,7 @@ def testForceQuote(self):
         self.assertEqual(shlex.quote("spam", force=True), "'spam'")
         self.assertEqual(shlex.quote("spam eggs", force=False), "'spam eggs'")
         self.assertEqual(shlex.quote("spam eggs", force=True), "'spam eggs'")
+        self.assertEqual(shlex.quote("two's-complement", force=False), "'two'\"'\"'s-complement'")
 
     def testJoin(self):
         for split_command, command in [