fix(google-maps): incorrect variable access for server-side rendering check (#19166)

We added a SSR check to the google-maps window info directive, but when
this PR landed in the patch branch, the variable names no longer
matched. The variable for the `_infoWindow` has been made public
with 3e00f4c, but this change did not
land in the patch branch as it targets a next minor release.

Author: devversion

src/google-maps/map-info-window/map-info-window.ts

@@ -117,7 +117,7 @@ export class MapInfoWindow implements OnInit, OnDestroy {
 
     // If no info window has been created on the server, we do not try closing it.
     // On the server, an info window cannot be created and this would cause errors.
-    if (this.infoWindow) {
+    if (this._infoWindow) {
       this.close();
     }
   }