website: Remove reference to the 'roadmap'

This document is out of date and no longer relevant. This has been
replaced by pointing users towards the Jira issue tracker.

Change-Id: I1b53c876483d3f4e2b82d3a3058f109ff94c4c7c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-website/+/55688
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