rel="noopener noreferrer" should be globally suppressed, not on a per-link basis

[brassy-endomorph]

Is your feature request related to a problem? Please describe.

We should not set the rel tag in HTML. There is no reason any website will ever need this info, and adding the rel per anchor tag manually will eventually lead to errors where we forget it and leak sensitive info.

Describe the solution you'd like

Have Flask globally set Referrer-Policy: no-referrer