empty-block: Fix false positive on select {}

[abhinav]

This fixes a false positive reported by revive on the following:

select {}

This is a way to block the program indefinitely.
It is used in cases like:

• Running a long-running server in a background thread
  and blocking main from exiting until the application dies.
  This is something you might do if your process has
  multiple servers/listeners in the same process.

  go grpcListenAndServe()
  go httpListenAndServe()
  go logFlusher()
  
  select {}

• In programs compiled to WASM to prevent the application from exiting,
  so that the Javascript components may interact with it.

  func main() {
    js.Global().Set("foo", foo)
    select {}
  }

  Without this, one may see an error like,
  "Error: Go program has already exited"

As a workaround, these programs can block forever
by receiving from a throwaway channel (<-make(chan struct{})),
but select {} is still a completely valid way of doing this,
so supporting it makes sense.

The issue was previously reported in #698 but was closed
because the author was satisfied with a //nolint comment.

Now that this rule is part of the default rule set (#799)
the case for addressing the false positive is stronger.

Resolves #804