Describe the bug

if you specify picks to ica_plot_sources the labels are in order starting with ICA0000, ICA0001....

For instance
ica.plot_sources(raw, picks=[4, 6])
will make a plot whose ch_name labels are ICA0000 ICA0001

Steps to reproduce

this is reproduced in the final plot of the ica example
https://mne.tools/dev/auto_examples/preprocessing/plot_run_ica.html#sphx-glr-auto-examples-preprocessing-plot-run-ica-py

CC @drammock