Remove the single convenience function we provided for StructDeclSyntax

This method survived from the early, early days of SwiftSyntax and does
not fit into the big picture anymore.

Author: ahoppen

Sources/SwiftSyntax/SyntaxNodes.swift.gyb

@@ -321,21 +321,6 @@ extension SyntaxNode {
 % end
 }
 
-/// MARK: Convenience methods
-
-extension StructDeclSyntax {
-  /// Creates a new StructDeclSyntax with the provided name as its identifier.
-  /// - param name: The new struct's name.
-  /// - returns: A new StructDeclSyntax with the same fields as the receiver,
-  ///            but with the provided identifier.
-  func withIdentifier(_ name: String) -> StructDeclSyntax {
-    let newToken = SyntaxFactory.makeIdentifier(name,
-      leadingTrivia: identifier.leadingTrivia,
-      trailingTrivia: identifier.trailingTrivia)
-    return withIdentifier(newToken)
-  }
-}
-
 extension SyntaxParser {
   static func verifyNodeDeclarationHash() -> Bool {
     return String(cString: swiftparse_syntax_structure_versioning_identifier()!) ==