Update default revocation fetch URL

[ctz]

This moves to using the alternative URL scheme introduced in #92

(We could also remove the backwards-compatible stuff it added here?)

[codspeed-hq]

Merging this PR will not alter performance

✅ 4 untouched benchmarks

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_{Comparing jbp-rev-fetch-url (d1a29d5) with main (e86596b)}

[djc]

(We could also remove the backwards-compatible stuff it added here?)

In the next PR after this maybe?