Ignore RC versions

**What happened**:
`go-struct-converter` had `v0.2.0-rc2`, chronicle misidentified the next version as `v0.2.1`. But more importantly, once `v0.2.0` is released, it should contain the full changelog from the prior non-rc release, as for all intents and purposes, that is what users are getting upgraded. It seems ignoring RC tags/releases altogether would address 2 issues at once.

**What you expected to happen**:
`v0.2.0` version is speculated, it has full change log from prior release (in this case `v0.1.0`)

**How to reproduce it (as minimally and precisely as possible)**:
Release an RC version as a `pre-release`, e.g.: https://github.com/anchore/go-struct-converter/releases/tag/v0.2.0-rc2, run chronicle.

Start by reproducing the issue with the linked v0.2.0-rc2 release and running chronicle, then trace the release and version-selection path that produces the v0.2.1 speculation. Compare the generated v0.2.0 changelog with the prior v0.1.0 release. Done means RC releases do not affect the next version or omit the full changes since the prior non-RC release.

Written by the indexing model from the issue text.