Update swift.yml (googleprojectzero#290)

Fix workflow definition.

Author: compnerd

.github/workflows/swift.yml

@@ -34,10 +34,10 @@ jobs:
     runs-on: windows-latest
 
     steps:
-      - uses: compnerd/gha-setup-swift
+      - uses: compnerd/gha-setup-swift@main
         with:
           branch: swift-5.5-release
-          tag: 5.5-release
+          tag: 5.5-RELEASE
       - uses: actions/checkout@v2
       - name: Build
         run: swift build -v