BTreeFolder2: do not patch manage_delAllObjects on Zope2

On Zope2 this method does not exist and this caused a test failure

======================================================================
FAIL: test_method_protection (testSecurity.TestSecurity)
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Traceback (most recent call last):
  File "parts/erp5/Products/ERP5/tests/testSecurity.py", line 110, in test_method_protection
    self.fail(message)
AssertionError:
The following 1 methods have a docstring but have no security assertions.
	parts/erp5/product/ERP5Type/patches/BTreeFolder2.py:111 manage_delAllObjects
32 jobs for erp5-vifib in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-TestRunner1

01:51:25

passed ERP5.PerformanceTest-TestRunner1

00:28:28

failed ERP5.UnitTest-TestRunner1

02:05:21

failed ERP5.UnitTest-Zope2-ForTestRunner1

02:04:16

passed ERP5.CodingStyleTest-TestRunner1

01:08:27

passed ERP5.PerformanceTest-TestRunner1

00:28:20

failed ERP5.UnitTest-TestRunner1

02:08:50

failed ERP5.UnitTest-TestRunner1

01:38:16

failed ERP5.UnitTest-TestRunner1

02:00:12

failed ERP5.UnitTest-TestRunner1

01:50:51

failed ERP5.UnitTest-TestRunner1

03:22:41

failed ERP5.UnitTest-TestRunner1

02:11:39

failed ERP5.UnitTest-TestRunner1

01:43:54

failed ERP5.UnitTest-TestRunner1

01:37:34

failed ERP5.UnitTest-TestRunner1

02:01:44

failed ERP5.UnitTest-TestRunner1

01:55:42

failed ERP5.UnitTest-TestRunner1

01:44:33

failed ERP5.UnitTest-TestRunner1

01:41:33

failed ERP5.UnitTest-TestRunner1

01:51:59

failed ERP5.UnitTest-Zope2-ForTestRunner1

02:28:27

failed ERP5.UnitTest-Zope2-ForTestRunner1

01:59:28

failed ERP5.UnitTest-Zope2-ForTestRunner1

02:03:56

failed ERP5.UnitTest-Zope2-ForTestRunner1

01:58:54

failed ERP5.UnitTest-Zope2-ForTestRunner1

02:07:50

failed ERP5.UnitTest-Zope2-ForTestRunner1

01:46:53

failed ERP5.UnitTest-Zope2-ForTestRunner1

02:14:10

failed ERP5.UnitTest-Zope2-ForTestRunner1

03:34:58

failed ERP5.UnitTest-Zope2-ForTestRunner1

01:57:31

failed ERP5.UnitTest-Zope2-ForTestRunner1

02:39:58

failed ERP5.UnitTest-Zope2-ForTestRunner1

03:54:22

failed ERP5.UnitTest-Zope2-ForTestRunner1

02:31:51

failed ERP5.UnitTest-Zope2-ForTestRunner1

02:11:18