Remove unnecessary helper function DateFmtLong (#24343)

After #24317 this function is only used in one place where it is not
needed. I confirmed the timestamp still renders correctly

Signed-off-by: Yarden Shoham <git@yardenshoham.com>

templates/admin/cron.tmpl

@@ -21,7 +21,7 @@
 						<td><button type="submit" class="ui green button" name="op" value="{{.Name}}" title="{{$.locale.Tr "admin.dashboard.operation_run"}}">{{svg "octicon-triangle-right"}}</button></td>
 						<td>{{$.locale.Tr (printf "admin.dashboard.%s" .Name)}}</td>
 						<td>{{.Spec}}</td>
-						<td>{{DateTime "full" (DateFmtLong .Next)}}</td>
+						<td>{{DateTime "full" .Next}}</td>
 						<td>{{if gt .Prev.Year 1}}{{DateTime "full" .Prev}}{{else}}N/A{{end}}</td>
 						<td>{{.ExecTimes}}</td>
 						<td {{if ne .Status ""}}data-tooltip-content="{{.FormatLastMessage $.locale}}"{{end}} >{{if eq .Status ""}}—{{else if eq .Status "finished"}}{{svg "octicon-check" 16}}{{else}}{{svg "octicon-x" 16}}{{end}}</td>