Remove unused hacking rule from HACKING.rst

This patch removes unused hacking M334 from HACKING.rst to avoid
confusing for new developers and also make the rule number in order.

Closes-Bug: #1539423
Change-Id: I79a791b39f7988254dd7fee1cb19dd16934475ae

HACKING.rst

@@ -8,19 +8,17 @@ Magnum Style Commandments
 Magnum Specific Commandments
 ----------------------------
 
+- [M302] Change assertEqual(A is not None) by optimal assert like
+  assertIsNotNone(A).
 - [M310] timeutils.utcnow() wrapper must be used instead of direct calls to
   datetime.datetime.utcnow() to make it easy to override its return value.
+- [M316] Change assertTrue(isinstance(A, B)) by optimal assert like
+  assertIsInstance(A, B).
 - [M318] Change assertEqual(A, None) or assertEqual(None, A) by optimal assert
   like assertIsNone(A)
 - [M322] Method's default argument shouldn't be mutable.
 - [M323] Change assertEqual(True, A) or assertEqual(False, A) by optimal assert
   like assertTrue(A) or assertFalse(A)
-- [M302] Change assertEqual(A is not None) by optimal assert like
-  assertIsNotNone(A).
-- [M316] Change assertTrue(isinstance(A, B)) by optimal assert like
-  assertIsInstance(A, B).
-- [M334] Change assertTrue/False(A in/not in B, message) to the more specific
-  assertIn/NotIn(A, B, message)
 - [M336] Must use a dict comprehension instead of a dict constructor
   with a sequence of key-value pairs.
 - [M338] Use assertIn/NotIn(A, B) rather than assertEqual(A in B, True/False).