Presubmit: remove NULL ban
Presubmit: remove NULL ban

It has too many false positives and gets in the way of
writing SQL-related test where NULL is a SQL NULL cell, not
a NULL pointer.

Change-Id: I12dd1b2cdeacfa1f2c3b5c5cb69783cfad1e14d5
google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto