sycl : fix test script (ggml-org#22737)

The error:
./examples/sycl/test.sh: line 122: level_zero:${$GGML_SYCL_DEVICE}: bad
substitution

was thrown whenever the user used this command:
./examples/sycl/test.sh -mg 0

Fix is to get rid of a dollar sign.

Author: dogunbound

examples/sycl/test.sh

@@ -119,7 +119,7 @@ if [ $GGML_SYCL_DEVICE -ne -1 ]; then
     echo "Use $GGML_SYCL_DEVICE as main GPU"
     #use signle GPU only
     GPUS_SETTING="-mg $GGML_SYCL_DEVICE -sm ${SPLIT_MODE}"
-    export ONEAPI_DEVICE_SELECTOR="level_zero:${$GGML_SYCL_DEVICE}"
+    export ONEAPI_DEVICE_SELECTOR="level_zero:${GGML_SYCL_DEVICE}"
     echo "ONEAPI_DEVICE_SELECTOR=${ONEAPI_DEVICE_SELECTOR}"
 else
     echo "Use all Intel GPUs, including iGPU & dGPU"