How can I remove the Ad Groups after removing Low Volume KWs?

Two ways. 1. Adwords Editor, sort by the warning symbols in upper left hand side of main window, while under ad groups. Delete all that have the error message in red, then post changes. 2. Adwords platform. Google notifications in upper right hand corner should prompt you to do something about all those ad groups and will take you to a screen where you can then delete them.

Update as of June 9:

Quicker way - Adwords Editor

Download the campaign - Get the Full Download - of the campaign you are working on.
Left Hand-side - Click on the campaign and the below, click on Ad groups.
At the top, in the input cell, click on the "Funnel" icon.
From the drop-down list find "Item-Level Filters" (you'll need to scroll down a little it's towards the bottom of the list).
Under "Item-Level Filters" select "Items With Warnings" (these have yellow triangle warning icons).
You now have a list of all the problem Ad groups - Select All - Remove - Check Changes - Post.
You are done. (start to finish - Checking Changes 2 mins max)