remove block-all-mixed-content from rocky, and error in deprecated

[underdarknl]

About this feature

Detailed description

Rocky was sending out deprecated csp directives.
We did not check on deprecated csp directives in our CSP header.

Feature benefit/User story

I want to be warned about deprecated csp directives.
KAT itself should not send out deprecated csp directives.

Design

This part should only be filled in by the OpenKAT design team.

Screenshots

Include screenshots of the proposed design changes here.

Possible solution

Outline your proposed solution for implementing the feature. You can include any specific ideas, designs, or functionalities here.

Alternatives considered

Describe any alternative approaches or solutions you've considered, and why you believe the proposed solution is superior.