Fix typo in inputs expression

Author: dtolnay

action.yml

@@ -34,7 +34,7 @@ runs:
         echo "::set-output name=components::$(for c in ${components//,/ }; do echo -n ' --component' $c; done)"
         echo "::set-output name=downgrade::${{inputs.toolchain == 'nightly' && inputs.components && ' --allow-downgrade' || ''}}"
       env:
-        targets: ${{inputs.targets || input.target || ''}}
+        targets: ${{inputs.targets || inputs.target || ''}}
         components: ${{inputs.components}}
       shell: bash