Fix closure error on `JSC_PRIMITIVE_OBJECT_DECLARATION`

when define type for primitives, should use `string` instead of `String`

Change-Id: I12d494c5256ec4dea99906190ad1229ca28d71c4

polygerrit-ui/app/elements/change-list/gr-user-header/gr-user-header.js

diff --git a/polygerrit-ui/app/elements/change-list/gr-user-header/gr-user-header.js b/polygerrit-ui/app/elements/change-list/gr-user-header/gr-user-header.js
index d9e9107..40f0b73 100644
--- a/polygerrit-ui/app/elements/change-list/gr-user-header/gr-user-header.js
+++ b/polygerrit-ui/app/elements/change-list/gr-user-header/gr-user-header.js
@@ -24,7 +24,7 @@
 
     static get properties() {
       return {
-      /** @type {?String} */
+      /** @type {?string} */
         userId: {
           type: String,
           observer: '_accountChanged',
@@ -48,7 +48,7 @@
           value: null,
         },
 
-        /** @type {?String} */
+        /** @type {?string} */
         _status: {
           type: String,
           value: null,