chore: update custom yarn step

Author: Qbandev

action.yml

@@ -85,10 +85,9 @@ runs:
       if: ${{ inputs.yarn-custom-url != '' }}
       env:
         COREPACK_ENABLE_UNSAFE_CUSTOM_URLS: 1
-        YARN_CUSTOM_URL: ${{ inputs.yarn-custom-url }}
       run: |
         echo "Preparing and activating custom Yarn from URL: ${YARN_CUSTOM_URL}"
-        corepack prepare "yarn@${YARN_CUSTOM_URL}" --activate
+        corepack prepare "yarn@${inputs.yarn-custom-url}" --activate
       shell: bash
 
     # In a low-risk environment, try to download cache of `node_modules`, if it