`regexpMust: for const patterns like v3PeerRegex, use regexp.MustCompile (gocritic)` linting error

This linting error was surfaced from an upgraded golangci-lint:

```log
internal/lockss/peers.go:82:25: regexpMust: for const patterns like v3PeerRegex, use regexp.MustCompile (gocritic)
	re, regExCompileErr := regexp.Compile(v3PeerRegex)
	                       ^
make: *** [Makefile:114: linting] Error 1
Error: Process completed with exit code 2.
```