Welcome to Android Central! Do you want to delete the Auto-Backup folder completely, both on your phone and in the cloud? Or do you just want to make it disappear from your phone only?
If you don't want the Google+ Auto Backup feature on, open your Photos app, tap Menu, then Settings, then Auto-Backup, and turn the switch to off.
If you just don't want the Auto-Backup folder to appear on your phone, go to Settings>Accounts-Google>[your Google account], and uncheck either Picasa, Gallery, or Google Photos (it may vary with the device). Be aware that Google Photos is different from Google+ Photos. The former syncs your Google+/Picasa cloud photos with the stock Gallery, while the latter syncs them with the Google+ Photos app.
If you want to get rid of the folder completely, then go to Google+ Photos on the web, select the Folder view, and delete the folder there. If it doesn't disappear from your Gallery app immediately, go to Settings>Apps>All (or the App Manager if you have Samsung), select Gallery, and Clear Cache/Clear Data, then force stop. When you open Gallery again, the database will rebuild, this time without the Auto-Backup folder.