DEVELOPERS: change Mathieu Audat's email address

Mathieu is no longer working at Savoir-faire Linux, update his email
address in the DEVELOPERS file.

Signed-off-by: Vivien Didelot <vivien.didelot@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

DEVELOPERS

@@ -1485,7 +1485,7 @@ F:	package/tslib/
 F:	package/x11r7/xdriver_xf86-input-tslib/
 F:	package/x11vnc/
 
-N:	Mathieu Audat <mathieu.audat@savoirfairelinux.com>
+N:	Mathieu Audat <mathieuaudat@gmail.com>
 F:	board/technologic/ts4900/
 F:	configs/ts4900_defconfig
 F:	package/ts4900-fpga/