tools/detect_targets.py using deprecated call mbedls.get_details_txt

[dhwalters423]

Calling mbed detect, causes the following WARNING:

WARNING:mbedls.lstools_base:Call to deprecated function get_details_txt. This method will be removed from the public API. Please use 'list_mbeds' instead

The relevant line is:

mbed-os/tools/detect_targets.py

Line 116 in 4d81ead

details_txt = mbeds.get_details_txt(mount_point)

This is related to this PR by me: #5077 so I am happy to submit a new PR to use the supported list_mbeds function instead. Incoming soon.

[dhwalters423]

Submitted #5715 awaiting review