Fix "press Enter key" message

The message said "Press any key to continue...", whereas only
Enter/Return is accepted.

PR #1783 <https://github.com/Genymobile/scrcpy/pull/1783>
Fixes #1757 <https://github.com/Genymobile/scrcpy/issues/1757>

Reviewed-by: Yu-Chen Lin <npes87184@gmail.com>
Signed-off-by: Romain Vimont <rom@rom1v.com>