This git configuration variable is deprecated in 2.36.0 onwards, so git
warns in the logs for every git call.
Luckily the default value has always been false[1], so we can just remove
this.
[ YOCTO #14939 ]
[1] aafe9fbaf4
(Bitbake rev: 8ad310633e0c5d5593631c1196cbdde30147efce)
Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>