Revert "RMX1921: Use Vulkan for UI rendering"

I can no longer trigger the renderthread Scudo crash mentioned
in https://github.com/kaderbava/device_realme_RMX1921/commit/5b0f6430f3c0e1439b0347655e23bd0f06d3ba75, so let's go back to the good old GL renderer. This
should also address the random video glitches in some apps including
but not limited to

- Instagram (after a recent update)
- Taobao/Alibaba
- Ding Ding

This reverts commit https://github.com/kaderbava/device_realme_RMX1921/commit/5b0f6430f3c0e1439b0347655e23bd0f06d3ba75

.

Signed-off-by: Chenyang Zhong <zhongcy95@gmail.com>
Signed-off-by: kaderbava <ksbava7325@gmail.com>