[SYCL][NFCI] Fix werror failure about unused field UrLoaderHandle (#22098)
Fixes a postcommit Win build
[error](https://github.com/intel/llvm/actions/runs/26280251772/job/77354368273).
Started after https://github.com/intel/llvm/pull/22031.
Signed-off-by: Nick Sarnie <nick.sarnie@intel.com>