DEVELOPERS: drop Guillaume Gardet, domain no longer exists

The oliseo.fr domain no longer responds to SMTP requests:

smtplib.SMTPRecipientsRefused: {'Guillaume Gardet <guillaume.gardet@oliseo.fr>': (550, b'5.1.2 <guillaume.gardet@oliseo.fr>: Recipient address rejected: Domain not found')}

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit e79c34a5214d574558406b96601273227a1b133d)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

DEVELOPERS

@@ -1021,11 +1021,6 @@ F:	package/python-redis/
 F:	package/python-rpi-ws281x/
 F:	package/python-wtforms/
 
-N:	Guillaume Gardet <guillaume.gardet@oliseo.fr>
-F:	package/c-icap/
-F:	package/c-icap-modules/
-F:	package/sdl2/
-
 N:	Guillaume William Brs <guillaume.bressaix@gmail.com>
 F:	package/liquid-dsp/
 F:	package/pixiewps/