src: fix vm_evt Tube on WHPX.

62e1b362a8 migrated the vm_evt Tubes out
of Config, but it looks like presubmit didn't catch the part that only
builds on WHPX. This CL makes the minor update so it builds again.

BUG=b:267219257
TEST=builds downstream

Change-Id: Ia4202571b95178240510d6fc76ec9f505c196183
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/4215672
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Commit-Queue: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-by: Vikram Auradkar <auradkar@google.com>

src/sys/windows.rs

@@ -1662,9 +1662,7 @@ fn run_config_inner(
                 no_smt,
                 apic_emulation_supported && irq_chip == IrqChipKind::Split,
                 cfg.force_calibrated_tsc_leaf,
-                cfg.vm_evt_wrtube
-                    .as_ref()
-                    .expect("vm_evt_wrtube must be set")
+                vm_evt_wrtube
                     .try_clone()
                     .expect("could not clone vm_evt_wrtube"),
             )?;