[SYCL][E2E] Remove DG2 XFAIL from discard_events_check_images.cpp (#16720)

It was failing on DG2 consistently in CI here but not internally, and I
found the problem was an old kernel driver and the fix was only
available in the new upstream driver in kernel 6.x, so I updated the Arc
runner to 24.04 and
[now](https://github.com/intel/llvm/actions/runs/12890654015/job/35943608796)
it's XPASSING

I cancelled precommit testing as this change will only be hit in
postcommit testing.

Signed-off-by: Sarnie, Nick <nick.sarnie@intel.com>

Author: sarnex

sycl/test-e2e/DiscardEvents/discard_events_check_images.cpp

@@ -1,9 +1,6 @@
 // UNSUPPORTED: hip
 // REQUIRES: aspect-ext_intel_legacy_image
 //
-// XFAIL: linux && gpu-intel-dg2
-// XFAIL-TRACKER: https://github.com/intel/llvm/issues/15812
-//
 // RUN: %{build} -o %t.out
 //
 // RUN: %{run} %t.out image