Settings: Fix crash when trashing storage in Site Details.

r565205 introduced a crash when deleting a site's used storage. Fix.

Bug: 852676
Cq-Include-Trybots: luci.chromium.try:closure_compilation
Change-Id: I8246cc478943dcfa47379ab6e9dfc61c14cae044
Reviewed-on: https://chromium-review.googlesource.com/1100673
Commit-Queue: Patti <patricialor@chromium.org>
Reviewed-by: Dave Schuyler <dschuyler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567939}

chrome/browser/resources/settings/site_settings/site_details.html

@@ -206,7 +206,7 @@
     </template>
     <website-usage-private-api id="usageApi"
         website-data-usage="{{storedData_}}"
-        website-storage-type="[[storageType_]]}">
+        website-storage-type="{{storageType_}}">
     </website-usage-private-api>
   </template>
   <script src="site_details.js"></script>