Fix window position in Tramp's shell-command

* lisp/net/tramp.el (tramp-handle-shell-command): Fix `window-start'
in output buffer.  (Bug#39171)
1 job for master in 56 minutes and 36 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #4985
test-all

00:56:36