ANDROID: GKI: Remove CONFIG_UBSAN_SIGNED_WRAP from gki_defconfig

In commit 984830d9 ("lib/Kconfig.ubsan: Remove 'default UBSAN' from
UBSAN_INTEGER_WRAP"), the dependancy on UBSAN was removed, so we can
remove the explicity "not set" value of CONFIG_UBSAN_SIGNED_WRAP from
the gki_defconfig files now.

This fixes the build as `savedefconfig` shows a difference without this.

Change-Id: I04c2e18746070ccfbfc02a7f790836a50d7e6e31
Fixes: 984830d9 ("lib/Kconfig.ubsan: Remove 'default UBSAN' from UBSAN_INTEGER_WRAP")
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>