[SourceKit] Add test case for rdar://64230277

rdar://64230277 seems to already be fixed. Add a test case for it.

Author: ahoppen

test/SourceKit/CursorInfo/rdar_64230277.swift

@@ -0,0 +1,9 @@
+// RUN: %sourcekitd-test -req=cursor -pos=5:16 %s -- %s | %FileCheck %s
+
+protocol View {}
+struct MyView: View {}
+func indicator<T>(_ a: T) -> some View {
+  MyView()
+}
+
+// CHECK: source.lang.swift.decl.generic_type_param