Drop --without-gnutls flag from curl

What does this MR do?

https://github.com/curl/curl/commit/68d89f242cf9f6326e3b2f6fe119b7c74ef41c66 dropped the use of --without-gnutls in favor of --with-* options. This commit actually had the opposite effect of enabling GnuTLS when --without-gnutls were set. https://github.com/curl/curl/pull/7994 fixes this behavior.

We can drop this now that this does completely the opposite of what it is supposed to be doing.

Discovered in !5592 (comment 731305703)

Checklist

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