ci: disable the windows tests until the runner can be stabilized again

I've been getting a stream of errors from Marge today like:

FAILED: src/gallium/drivers/llvmpipe/lp_test_conv.exe
link @src/gallium/drivers/llvmpipe/lp_test_conv.exe.rsp
LINK : fatal error LNK1102: out of memory
[1080/1141] Compiling C object src/gallium/frontends/wgl/945cc3d@@wgl@sta/stw_getprocaddress.c.obj

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5534>
1 file changed