fix: keep the lead char when editing an existing link (#17667)

Author: iOvergaard

src/Umbraco.Web.UI.Client/src/common/services/tinymce.service.js

@@ -1216,10 +1216,9 @@ function tinyMceService($rootScope, $q, imageHelper, $locale, $http, $timeout, s
             target: anchor.attr("target")
           };
 
-          // drop the lead char from the anchor text, if it has a value
           var anchorVal = anchor[0].dataset.anchor;
           if (anchorVal) {
-            currentTarget.anchor = anchorVal.substring(1);
+            currentTarget.anchor = anchorVal;
           }
 
           //locallink detection, we do this here, to avoid poluting the editorService