Remove checking for error from session end in web terminal (#8797)
Remove checking for error from session end in web terminal (#8797)

Removes the call for wait for ssh.Session end to check for errors
in web terminal which fixes a regression bug where typing "exit" 
in web terminal does not return session end event. 
PR #8081 removed the need to check for errors as it correctly 
returns exit errors whereas before it returned nil. 
gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport