Update CHANGELOG.md (#3079)

Author: Chuan Ren

Firebase/Auth/CHANGELOG.md

@@ -1,3 +1,6 @@
+# v6.1.1
+- Fix an issue where a user can't link with email provider by email link. (#3030)
+
 # v6.1.0
 - Add support of web.app as an auth domain. (#2959)
 - Fix an issue where the return type of `getStoredUserForAccessGroup:error:` is nonnull. (#2879)