Remove comment about extension backwards compat
Remove comment about extension backwards compat

0.7 was a long time ago; there's no reason for extension to supports such old versions.
drewja/flask,mitsuhiko/flask,mitsuhiko/flask,fkazimierczak/flask,pallets/flask,fkazimierczak/flask,pallets/flask,pallets/flask,fkazimierczak/flask,drewja/flask,drewja/flask