DEVELOPERS: remove Jonathan Liu

In a private e-mail answering one of our notifications about packages
being outdated, Jonathan replied:

"""
I switched from Buildroot to OpenEmbedded in 2013 so am no longer actively
involved with Buildroot.
Please unsubscribe me from outdated package notifications.
"""

So let's remove him from the DEVELOPERS file.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

DEVELOPERS

@@ -1237,10 +1237,6 @@ F:	package/phidgetwebservice/
 F:	package/rapidxml/
 F:	package/sphinxbase/
 
-N:	Jonathan Liu <net147@gmail.com>
-F:	package/python-meld3/
-F:	package/supervisor/
-
 N:	Joris Offouga <offougajoris@gmail.com>
 F:	package/python-colorlog/
 F:	package/python-simplelogging/