fixed syntax in ymal file

Author: Malmahrouqi3

.github/workflows/bench.yml

@@ -39,7 +39,7 @@ jobs:
             group: frontier
             labels: olcf
             flag: f
-            device: ['gpu']
+            device: gpu
             build_script: "bash .github/workflows/frontier/build.sh ${{ matrix.device }}"
     runs-on:
       group: ${{ matrix.group }}