Bump docs workflow to Swift 6 too

Author: fwcd

.github/workflows/docs.yml

@@ -26,10 +26,10 @@ jobs:
     - name: Set up Pages
       uses: actions/configure-pages@v5
     - name: Set up Swift
-    # https://github.com/swift-actions/setup-swift/pull/680
-      uses: swift-actions/setup-swift@bb83339d1e8577741bdc6c65ba551ce7dc0fb854
+    # https://github.com/swift-actions/setup-swift/pull/684
+      uses: swift-actions/setup-swift@736b146b8f26e7a66cbe3a89bc8d413ac0ea536e
       with:
-        swift-version: '5.10'
+        swift-version: '6.0'
     - name: Generate Docs
       uses: fwcd/swift-docc-action@v1
       with: