Fix action runner last online state on edit page (go-gitea#25337)

Backport fix for action runner last online state not showing in
`release/v1.20` - fixes go-gitea#25336

Author: derelm

templates/shared/actions/runner_edit.tmpl

@@ -13,7 +13,7 @@
 				</div>
 				<div class="field gt-dib gt-mr-4">
 					<label>{{.locale.Tr "actions.runners.last_online"}}</label>
-					<span>{{if .LastOnline}}{{TimeSinceUnix .LastOnline $.locale}}{{else}}{{$.locale.Tr "never"}}{{end}}</span>
+					<span>{{if .Runner.LastOnline}}{{TimeSinceUnix .Runner.LastOnline $.locale}}{{else}}{{$.locale.Tr "never"}}{{end}}</span>
 				</div>
 				<div class="field gt-dib gt-mr-4">
 					<label>{{.locale.Tr "actions.runners.agent_labels"}}</label>