Fix a typo in comment

Author: StevenWong12

CodeGeneration/Sources/SyntaxSupport/AvailabilityNodes.swift

@@ -149,8 +149,8 @@ public let AVAILABILITY_NODES: [Node] = [
     omitWhenEmpty: true
   ),
 
-  // version-tuple -> integer-literal version-tuple-element?
-  //                      | float-literal version-tuple-element?
+  // version-tuple -> integer-literal version-list?
+  //                      | float-literal version-list?
   Node(
     name: "VersionTuple",
     nameForDiagnostics: "version tuple",