Update versioning background to reflect CalVer adoption

[ahouseholder]

Describe the bug

The text of https://certcc.github.io/Vultron/topics/background/versioning/ is incongruous with our Year.Month.micro versioning scheme.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://certcc.github.io/Vultron/topics/background/versioning/
2. Observe that it describes a SemVer rather than CalVer scheme

Expected behavior

The text should describe the CalVer scheme we've adopted.

[sei-renae]

The existing semver is buggy as is