website: Replace master with stable in the getting started page

The master branch is an old unused branch and users might
mistakenly check it out

Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Change-Id: I755393190070125b8e8356e85d01a13d94587b4b
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-website/+/53783
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: Jason Lowe-Power <power.jg@gmail.com>
1 file changed