[Docs] Fix DocC warnings in FirebaseSharedSwift (#14033)

Author: ncooke3

FirebaseSharedSwift/Sources/third_party/FirebaseDataEncoder/FirebaseDataEncoder.swift

@@ -1225,7 +1225,7 @@ public class FirebaseDataDecoder {
   /// Decodes a top-level value of the given type from the given JSON representation.
   ///
   /// - parameter type: The type of the value to decode.
-  /// - parameter data: The data to decode from.
+  /// - parameter structure: The data to decode from.
   /// - returns: A value of the requested type.
   /// - throws: `DecodingError.dataCorrupted` if values requested from the payload are corrupted, or if the given data is not valid JSON.
   /// - throws: An error if any value throws an error during decoding.