remove mention of unsupported Safari browser

See:

• https://gitlab.cee.redhat.com/red-hat-developers-documentation/red-hat-devtools/-/merge_requests/1257
• https://issues.redhat.com/browse/CRW-2083

The solution proposed in th MR is good, but we need an implementation upstream.

Verify the support state of Safari in upstream:

• Safari is supported upstream but not supported downstream => use an attribute to differentiate upstream and downstream.
• Safari is not supported both upstream and downstream => remove mention to Safari.