Update the branch for swift-format to swift-5.5-branch

Author: shahmishal

utils/update_checkout/update-checkout-config.json

@@ -109,7 +109,7 @@
                  "cmake": "v3.16.5",
                  "indexstore-db": "release/5.5",
                  "sourcekit-lsp": "release/5.5",
-                 "swift-format": "main"
+                 "swift-format": "swift-5.5-branch"
              }
         },
         "concurrency-5.5-abi-2": {