x/vulndb: remove GO-2021-0143 which is a duplicate of GO-2021-0226

Change-Id: Ie8b0a17a46d9c6733d166639ff8024e3a388bf1a
Reviewed-on: https://go-review.googlesource.com/c/vulndb/+/418596
Reviewed-by: Damien Neil <[email protected]>
Reviewed-by: Tatiana Bradley <[email protected]>

Author: tatianab