remove notice

[romainmenke]

This removes the notice that postcss-preset-env should be updated. At this time this message served its purpose.

It created awareness that there was an urgent need to update.

Those that haven't updated either :

• really can not or do not want to update
• use another plugin that bundles postcss-preset-env (e.g. precss)
• do not know how to use their package manager

We have now also move beyond version 7.x and the latest release is 9.2.0.

I don't think the message is useful anymore but it does still cause noise for users and for us.