Unpin libcurl in conda build

[phoebusm]

libcurl is pinned in conda build in https://github.com/man-group/ArcticDB/pull/1338 due to the behaviour changes in different build of libcurl, e.g. https://github.com/curl/curl/blob/b935fd4a07aa9dc0fa352b0a1d4822c4d901577b/lib/vtls/openssl.c#L4767. The issue starts affecting us since v8.6.0. Release build is needed in conda. Issue is raised in the feedstock repo. If the maintainers refuse to do so, we may need to have our own libcurl release build feedstock.