Changing ciphers used by certs generated for web-platform-tests

Servo is investigating how plausible it is to remove support for some older
ciphers listed under "intermediate compatibility" on
https://wiki.mozilla.org/Security/Server_Side_TLS . We discovered that the
certs generated by the WPT setup make use of these, so we proposing
updating that to use a more modern one instead (ECDSA with curve
secp521r1). Any objections to us upstreaming the changes in
https://github.com/servo/servo/pull/16535/commits/64ee14ba92d4e8566ce19ecd63804d5d3d4a38e4
?

Cheers,
Josh