[CI][Bench] Don't build and install "custom" UR in workflow (#21517)
Reuse already built SYCL instead. From time to time this was causing
issues of mismatched SYCL and UR.
We've built UR on our own, as there's no UR's cmake files delivered in
the "toolchain".
We fixed that on Compute Benchmarks side so now just ur libs and headers
are required.