Remove test_malloc_implicit. NFC (#24774)

This test was added back in ac0354b to test the automatic dependency
between getenv and malloc.

These days this is all in native code so I don't think this test serves
any purpose anymore.

Author: sbc100

test/other/test_malloc_implicit.cpp

@@ -6337,9 +6337,6 @@ def test_dashM_respect_dashO(self):
     self.assertEqual(len(with_dash_o), 0)
     self.assertNotEqual(len(without_dash_o), 0)
 
-  def test_malloc_implicit(self):
-    self.do_other_test('test_malloc_implicit.cpp')
-
   def test_switch64phi(self):
     # issue 2539, fastcomp segfault on phi-i64 interaction
     create_file('src.cpp', r'''