Update configure-rootfs anchor for typo.

[samueldr]

This part

Consider skimming the rootfs section and the global section of the installation docs to understand the significance of this (then return here).

was referencing to #configure-rootfs already. A quick ag on the repo did not find any other internal reference to the #configure-roofs typo, but this might break external links. In the event the external links are more important than correctness, the fix should instead change that link to use the erroneous #configure-roofs.

[paradigm]

Good catch. I'm not overly concerned that there are existing links out there to that point - may as well correct it here and now. Thanks!