scripts: west_commands: runners: do not print newline in telnet decode

Remove the newline printed after decoding a block of telnet data from
the server in the "pure python" implementation used when netcat is not
available. This newline print is incorrect as it is not in the RTT
output being produced from the device, and can impact programs like
twister which expect specific strings in the output and cannot handle
these strings being split across two lines

Signed-off-by: Daniel DeGrasse <ddegrasse@tenstorrent.com>