Update method deprecation messages and add changelog (#12122)

Author: renkelvin

FirebaseAuth/CHANGELOG.md

@@ -1,3 +1,6 @@
+# 10.19.0
+- [changed] Deprecate `updateEmail(to email: String)` and `fetchSignInMethods(forEmail email: String)`. (#12081)
+
 # 10.18.0
 - [fixed] Fix a bug where anonymous account can't be linked with email password credential. (#11911)
 

FirebaseAuth/Sources/Public/FirebaseAuth/FIRAuth.h

@@ -397,7 +397,8 @@ NS_SWIFT_NAME(Auth)
                         completion:(nullable void (^)(NSArray<NSString *> *_Nullable,
                                                       NSError *_Nullable))completion
     DEPRECATED_MSG_ATTRIBUTE(
-        "This method returns an empty list when Email Enumeration Protection is enabled.");
+        "This method is deprecated and will be removed in a future release. This method returns an "
+        "empty list when Email Enumeration Protection is enabled.");
 
 /** @fn signInWithEmail:password:completion:
     @brief Signs in using an email address and password. When [Email Enumeration

FirebaseAuth/Sources/Public/FirebaseAuth/FIRUser.h

@@ -162,8 +162,9 @@ NS_SWIFT_NAME(User)
  */
 - (void)updateEmail:(NSString *)email
          completion:(nullable void (^)(NSError *_Nullable error))completion
-    NS_SWIFT_NAME(updateEmail(to:completion:))
-        DEPRECATED_MSG_ATTRIBUTE("Use sendEmailVerificationBeforeUpdatingEmail: instead.");
+    NS_SWIFT_NAME(updateEmail(to:completion:)) DEPRECATED_MSG_ATTRIBUTE(
+        "This method is deprecated and will be removed in a future release. Use "
+        "sendEmailVerification(beforeUpdatingEmail email: String) instead.");
 
 /** @fn updatePassword:completion:
     @brief Updates the password for the user. On success, the cached user profile data is updated.