defconfig: arm64: Remove QTEE_SHM_BRIDGE

QTEE_SHM_BRIDGE is selected by QCOM_SCM in commit 1ad129ee
("firmware: shmbridge: Enable shmbridge by default"), so do not need to
explicitly mention in defconfig.

Change-Id: Idef45619a28990e502a985724d7249707a208d3a
Signed-off-by: Elliot Berman <eberman@codeaurora.org>