Alias gripping_sheets -> sheet_grab

BUR #28149 has been rejected.

create alias gripping_sheets -> sheet_grab

I'm used to it being called that.

None of the other grab tags has a grip alias, so I'm not sure about the actual utility of this.

This bulk update request is pending automatic rejection in 5 days.

This bulk update request has been rejected because it was not approved within 45 days.

The bulk update request #28149 (forum #291146) has been rejected by @DanbooruBot.