[NFC][Clang] Remove spurious forward slashes. (#19412)

Having them in the comments seems unnecessary.

Author: bader

clang/lib/Driver/ToolChains/SYCL.h

@@ -222,7 +222,7 @@ StringRef resolveGenDevice(StringRef DeviceName);
 SmallString<64> getGenDeviceMacro(StringRef DeviceName);
 StringRef getGenGRFFlag(StringRef GRFMode);
 
-// // Prefix for GPU specific targets used for -fsycl-targets
+// Prefix for GPU specific targets used for -fsycl-targets
 constexpr char IntelGPU[] = "intel_gpu_";
 constexpr char NvidiaGPU[] = "nvidia_gpu_";
 constexpr char AmdGPU[] = "amd_gpu_";