Update the branch to main for swift-tools-support-core

Author: shahmishal

utils/update_checkout/update-checkout-config.json

@@ -61,7 +61,7 @@
                 "swift": "master",
                 "cmark": "main",
                 "llbuild": "main",
-                "swift-tools-support-core": "master",
+                "swift-tools-support-core": "main",
                 "swiftpm": "master",
                 "swift-argument-parser": "0.3.0",
                 "swift-driver": "master",
@@ -91,7 +91,7 @@
                 "swift": "master-next",
                 "cmark": "main",
                 "llbuild": "main",
-                "swift-tools-support-core": "master",
+                "swift-tools-support-core": "main",
                 "swiftpm": "master",
                 "swift-argument-parser": "0.3.0",
                 "swift-driver": "master",
@@ -314,7 +314,7 @@
                 "swift": "master-rebranch",
                 "cmark": "main",
                 "llbuild": "main",
-                "swift-tools-support-core": "master",
+                "swift-tools-support-core": "main",
                 "swiftpm": "master",
                 "swift-argument-parser": "0.3.0",
                 "swift-driver": "master",