fix: set sharded true if WORLD_SIZE is set

[drbh]

This is a tiny PR that simply set assumes sharded is true if a WORLD_SIZE env is set.

Adding because I wasted time debugging when I just forgot to set --sharded along with the WORLD_SIZE and RANK env vars. This PR allows --sharded to be inferred and is for dev convenience

note** we already do this in the launcher

text-generation-inference/launcher/src/main.rs

Lines 518 to 521 in 11ea9ce

	// Activate tensor parallelism
	if world_size > 1 {
	shard_args.push("--sharded".to_string());
	}

but this avoids the issue if you are running the server/router separately

[Narsil]

Not a huge fan tbh.

All of this is supposed to be handled by the launcher which shouldn't make any mistake.
I understand the inconvenience, but this seems like opening up a new class of bugs for relatively little benefit. (Because WORLD_SIZE could be defined by somehow else than the launcher).

Let's see how the others feel about this.

[drbh]

Closing since this change is unneeded and it does not seem like others are interested at the moment. Will revisit if interest arises