Do not force /bin/sh for /etc/qubes-rpc/qubes.GetAppmenus

Call it as normal executable instead of forcing it through /bin/sh.
Especially when now it have bash shebang.

Fixes QubesOS/qubes-issues#4417

misc/qubes-trigger-sync-appmenus.sh

@@ -5,5 +5,5 @@
 . /usr/lib/qubes/init/functions
 
 if is_updateable ; then
-    /usr/lib/qubes/qrexec-client-vm dom0 qubes.SyncAppMenus /bin/sh /etc/qubes-rpc/qubes.GetAppmenus
+    /usr/lib/qubes/qrexec-client-vm dom0 qubes.SyncAppMenus /etc/qubes-rpc/qubes.GetAppmenus
 fi