reverts the umb-button change

src/Umbraco.Web.UI.Client/src/common/directives/components/buttons/umbbutton.directive.js

@@ -102,8 +102,7 @@ Use this directive to render an umbraco button. The directive can be used to gen
                 showCaret: "@?",
                 autoFocus: "@?",
                 hasPopup: "@?",
-                isExpanded: "<?",
-                submitValue: "@?"
+                isExpanded: "<?"
             }
         });
 

src/Umbraco.Web.UI.Client/src/views/components/buttons/umb-button.html

@@ -43,7 +43,6 @@
     <button
         ng-if="vm.type === 'submit'"
         type="submit"
-        value="{{vm.submitButton}}"
         class="btn umb-button__button {{vm.style}} umb-button--{{vm.size}} umb-outline"
         hotkey="{{vm.shortcut}}"
         hotkey-when-hidden="{{vm.shortcutWhenHidden}}"

src/Umbraco.Web/Security/BackOfficeExternalLoginProviderOptions.cs

@@ -16,9 +16,7 @@ namespace Umbraco.Web.Security
         /// When specified this will be called to retrieve the <see cref="AuthenticationProperties"/> used during the authentication Challenge response.
         /// </summary>
         /// <remarks>
-        /// For example, when trying to implement an Azure AD B2C provider or other OAuth provider that requires a customized Challenge Result in order to work then
-        /// this must be used.
-        /// See: http://issues.umbraco.org/issue/U4-7353
+        /// This will generally not be needed since OpenIdConnect.RedirectToIdentityProvider options should be used instead
         /// </remarks>
         [IgnoreDataMember]
         public Func<IOwinContext, AuthenticationProperties> OnChallenge { get; set; }