muster release v5.23.4

The Go module is github.com/giantswarm/muster/v5; every import path carries the suffix (github.com/giantswarm/muster/v5/pkg/oauth). The module path had no /v5 while the releases were v5.x, and Go only considers v0 and v1 tags for such a path: go install github.com/giantswarm/muster@latest resolved to v1.12.0 from August and installed a month-old v1 binary, and go install github.com/giantswarm/muster@v5.23.2 was refused (“module contains a go.mod file, so module path must match major version”). go install github.com/giantswarm/muster/v5@latest now resolves to the newest release, and Go’s own VCS stamping gives a build of a tagged commit its v5 tag instead of a pseudo-version of the last v1 tag. No repository outside this one imported the old path. The goimports -local prefix of the pre-commit hook and the contributor docs follow the module. The OpenTelemetry scope name github.com/giantswarm/muster (observability.TracerName, the otel_scope_name label, the logger scope) is an identifier dashboards filter on, not an import path, and is unchanged.