kconfig: openthread: Increase range for OPENTHREAD_CLI_MAX_LINE_LENGTH

This commit increases the range of value for the
OPENTHREAD_CLI_MAX_LINE_LENGTH option to the maximum allowed.

The previous range may have been insufficient for Openthread vendor CLI
commands.

Signed-off-by: Lukasz Maciejonczyk <lukasz.maciejonczyk@nordicsemi.no>