Set GOMAXPROCS only when badger is used.

[maeb]

https://github.com/nlnwa/warchaeology/blob/606d0dcc55be3134b6c819c1ba87907a37a71264/main.go#L33

This setting should be localized to the cases where badger is used as it is badger who recommends the value to be 128 or higher (see https://dgraph.io/docs/badger/get-started/ and https://dgraph.io/docs/badger/faq/#are-there-any-go-specific-settings-that-i-should-use).