[5.5] Add support for release/5.5 branch in update-checkout script

Author: shahmishal

utils/update_checkout/update-checkout-config.json

@@ -84,6 +84,34 @@
                 "swift-format": "main"
             }
         },
+        "release/5.5": {
+             "aliases": ["release/5.5", "swift/release/5.5"],
+             "repos": {
+                 "llvm-project": "swift/release/5.5",
+                 "swift": "release/5.5",
+                 "cmark": "release/5.5",
+                 "llbuild": "release/5.5",
+                 "swift-tools-support-core": "release/5.5",
+                 "swiftpm": "release/5.5",
+                 "swift-argument-parser": "0.4.1",
+                 "swift-crypto": "1.1.5",
+                 "swift-driver": "release/5.5",
+                 "swift-syntax": "release/5.5",
+                 "swift-stress-tester": "release/5.5",
+                 "swift-corelibs-xctest": "release/5.5",
+                 "swift-corelibs-foundation": "release/5.5",
+                 "swift-corelibs-libdispatch": "release/5.5",
+                 "swift-integration-tests": "release/5.5",
+                 "swift-xcode-playground-support": "release/5.5",
+                 "ninja": "release",
+                 "icu": "release-65-1",
+                 "yams": "4.0.2",
+                 "cmake": "v3.16.5",
+                 "indexstore-db": "release/5.5",
+                 "sourcekit-lsp": "release/5.5",
+                 "swift-format": "main"
+             }
+        },
         "rebranch": {
             "aliases": ["rebranch", "swift/rebranch"],
             "repos": {