func_frame_trace: Remove bogus assertion.

The FRAME_TRACE function currently asserts if it sees
a MASQUERADE_NOTIFY. However, this is a legitimate thing
that can happen so asserting is inappropriate, as there
are no clear negative ramifications of such a thing. This
is adjusted to be like the other frames to print out
the subclass.

ASTERISK-30210 #close

Change-Id: I8ecbdcf17e35f64bdeab42868471f581ad1d1a56