ANDROID: GKI defconfig: Remove ZRAM from gki defconfig

Allow vendors to provide zram module in vendor fragment
for GKI 2.0 since modules can't be overridden

Bug: 150917000
Test: boot check for swap (expected none).
      adb shell cat /proc/swaps
      adb shell grep Swap /proc/meminfo
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Change-Id: Ic346c6e4a1cdd975fa0c51bde9282ef0e32963f1