chore: modify test action

[skip ci]

.github/actions/notify/action.yaml

@@ -19,6 +19,7 @@ inputs:
   image_url:
     description: "The URL of the image to be included in the notification."
     required: false
+    default: 'https://cdn.jsdelivr.net/npm/simple-icons@v16/icons/git.svg'
 
   event_author:
     description: "The author of the event."
@@ -84,7 +85,7 @@ runs:
         PAYLOAD=$(jq -n -r \
           --arg header "${{ inputs.title }}" \
           --arg subtitle "${{ inputs.subtitle || '' }}" \
-          --arg imgurl "${{ inputs.image_url || 'https://cdn.jsdelivr.net/gh/homarr-labs/dashboard-icons/png/git.png' }}" \
+          --arg imgurl "${{ inputs.image_url }}" \
           --arg title "${{ inputs.event_title || 'no event title given' }}" \
           --arg body "${{ inputs.event_body || 'no event body given' }}" \
           --arg author "${{ inputs.event_author || 'no event author given' }}" \