Update default.xml

migrate swift-corelibs-libdispatch to swiftlang as the repository has migrated

Author: compnerd

default.xml

@@ -17,7 +17,7 @@
   <project remote="github" name="apple/swift-certificates" path="swift-certificates" revision="refs/tags/1.0.1" />
   <project remote="github" name="swiftlang/swift-cmark" path="cmark" revision="gfm" />
   <project remote="github" name="apple/swift-collections" path="swift-collections" revision="refs/tags/1.1.3" />
-  <project remote="github" name="apple/swift-corelibs-libdispatch" path="swift-corelibs-libdispatch" />
+  <project remote="github" name="swiftlang/swift-corelibs-libdispatch" path="swift-corelibs-libdispatch" />
   <project remote="github" name="swiftlang/swift-corelibs-foundation" path="swift-corelibs-foundation" />
   <project remote="github" name="swiftlang/swift-corelibs-xctest" path="swift-corelibs-xctest" />
   <project remote="github" name="apple/swift-crypto" path="swift-crypto" revision="refs/tags/3.0.0" />