[CI][Benchmarks] fix wgc param in UllsEmptyKernel (#18624)

Author: PatKamin

devops/scripts/benchmarks/benches/compute.py

@@ -748,7 +748,7 @@ def bin_args(self) -> list[str]:
         return [
             "--iterations=10000",
             f"--wgs={self.wgs}",
-            f"--wgc={self.wgs}",
+            f"--wgc={self.wgc}",
         ]