Make SyntaxChildrenIndexData internal

Author: ahoppen

Sources/SwiftSyntax/SyntaxChildren.swift

@@ -14,7 +14,7 @@
 
 /// The data for an index in a syntax children collection that is not the end
 /// index. See `SyntaxChildrenIndex` for the representation of the end index.
-public struct SyntaxChildrenIndexData: Comparable {
+struct SyntaxChildrenIndexData: Comparable {
   /// The UTF-8 offset of the item at this index in the source file
   /// See `AbsoluteSyntaxPosition.offset`
   let offset: UInt32
@@ -25,7 +25,7 @@ public struct SyntaxChildrenIndexData: Comparable {
   /// See `SyntaxIdentifier.indexIntree`
   let indexInTree: SyntaxIndexInTree
 
-  public static func < (
+  static func < (
     lhs: SyntaxChildrenIndexData,
     rhs: SyntaxChildrenIndexData
   ) -> Bool {