Revert "build: add test-gl-renderer option"
This reverts commit 1618697d.
The original commit was a workaround for mesa/mesa#2219 (closed) which was fixed in Mesa:
- c7617d8908a970124321ce731b43d5996c3c5775 released as 20.1.0-rc1
- a0e6341fe4417e41cda0b19e4fa7f8bbe4e1dba1 released as 19.3.5
- f27e5d9df5bc9c85d45c2cb1f2a4997b453365fe released as 20.0.0
This workaround should not be necessary anymore, we don't use it in our CI, and it was manual to begin with. Therefore remove it.