Bluetooth: Mesh: Use default provisioning protocol timeout in RPR Client

The timeout used upon opening the link with the server relates to the
PB-Remote Link Open procedure, but not to the whole provisioning
procedure. For the provisioning procedure, the timeout should be at
least 60 seconds as explained in section 5.4.4.

Signed-off-by: Pavel Vasilyev <pavel.vasilyev@nordicsemi.no>