remove workaround for `v1/groups` endpoint

[toph-allen]

The get_groups() function has a workaround for a pagination quirk in Connect's v1/groups API, which always returns the first page of results when a prefix is specified.

This bug is tracked in the Connect repo: https://github.com/rstudio/connect/issues/28774

When that's resolved, we should remove the workaround: #326 (comment)

[nealrichardson]

The groups API will support pagination in 2025.04.0, but we don't want to just revert #326 because we'll still need that for compatibility with older versions. So we'll want to do things differently based on the Connect server version.