Revert "Modifies the front page with the Least Square example."

This reverts commit e542100bd96eefae8e731ebeb5a52cdef62c77be.

Ping @MelodyLucid: I reverted the change since the graph shows
the fact that the slowdown is related to the excessive heap use
when using generic classes, but I'm sure we still do some boxing
on the critical path. Let's revert for now and spend figure out
what's happening.