Update swift-corelibs-xctest to main branch

Author: shahmishal

utils/update_checkout/update-checkout-config.json

@@ -67,7 +67,7 @@
                 "swift-driver": "main",
                 "swift-syntax": "main",
                 "swift-stress-tester": "master",
-                "swift-corelibs-xctest": "master",
+                "swift-corelibs-xctest": "main",
                 "swift-corelibs-foundation": "master",
                 "swift-corelibs-libdispatch": "master",
                 "swift-integration-tests": "master",
@@ -97,7 +97,7 @@
                 "swift-driver": "main",
                 "swift-syntax": "main",
                 "swift-stress-tester": "main",
-                "swift-corelibs-xctest": "master",
+                "swift-corelibs-xctest": "main",
                 "swift-corelibs-foundation": "master",
                 "swift-corelibs-libdispatch": "master",
                 "swift-integration-tests": "master",
@@ -320,7 +320,7 @@
                 "swift-driver": "main",
                 "swift-syntax": "main",
                 "swift-stress-tester": "main",
-                "swift-corelibs-xctest": "master",
+                "swift-corelibs-xctest": "main",
                 "swift-corelibs-foundation": "master",
                 "swift-corelibs-libdispatch": "master",
                 "swift-integration-tests": "master",