fix: update quoting around labels when adding label

Fixes #432

action.yml

@@ -161,7 +161,7 @@ runs:
         # If the label does not exist, create it before adding it to the PR in the format 'tf:${{ inputs.command }}'.
         gh api /repos/${{ github.repository }}/labels/tf:${{ inputs.command }} --header "$GH_API" --method GET || \
           gh api /repos/${{ github.repository }}/labels --header "$GH_API" --method POST --field "name=tf:${{ inputs.command }}" --field "description=Pull requests that ${{ inputs.command }} TF code." --field "color=5C4EE5"
-        gh api /repos/${{ github.repository }}/issues/${{ steps.identifier.outputs.pr }}/labels --header "$GH_API" --method POST --field "labels[]=tf:${{ inputs.command }}"
+        gh pr edit ${{ steps.identifier.outputs.pr }} --label "tf:${{ inputs.command }}" ${{ github.repository }}
 
     - if: ${{ inputs.command == 'plan' }}
       id: plan