Remove `noopener` on external link anchors

Created by: gergelypap

As of 2021, the spec have changed on how target="_blank" anchor elements use openers. The usage of rel="noreferrer" implies noopener as well by default. See the spec mentioning this: https://html.spec.whatwg.org/multipage/links.html#link-type-noreferrer

We should remove noopener on target="_blank" anchors, as there is no need to include it anymore. It can be tested on https://mathiasbynens.github.io/rel-noopener/

The react/jsx-no-target-blank lint rule is fine with only including noreferrer as the value.