docs: fix NSDictionary in firebaseFunctions internal sources (#14965)

Author: MojtabaHs

FirebaseFunctions/Sources/Internal/FunctionsSerializer.swift

@@ -29,7 +29,7 @@ final class FunctionsSerializer: Sendable {
  // - NSNull (note: `nil` collection values from a Swift caller will be treated as NSNull)
  // - NSNumber
  // - NSString
- // - NSDicionary
+ // - NSDictionary
  // - NSArray
  func encode(_ object: Any) throws -> Any {
  if object is NSNull {
@@ -58,7 +58,7 @@ final class FunctionsSerializer: Sendable {
  // - NSNull (note: `nil` collection values from a Swift caller will be treated as NSNull)
  // - NSNumber
  // - NSString
- // - NSDicionary
+ // - NSDictionary
  // - NSArray
  func decode(_ object: Any) throws -> Any {
  // Return these types as is. PORTING NOTE: Moved from the bottom of the func for readability.