Fix link to FLUX model in README (#1978)

Author: rm-wu

README.md

@@ -24,7 +24,7 @@
 - [2025/07] We published [instructions](/torchtitan/models/README.md) on how to add a model to `torchtitan`.
 - [2025/07] We released `torchtitan` [v0.1.0](https://github.com/pytorch/torchtitan/releases), and also set up nightly builds.
 - [2025/04] Our paper was accepted by [ICLR 2025](https://iclr.cc/virtual/2025/poster/29620).
-- [2025/04] Training the diffusion model [FLUX](torchtitan/experiments/flux/) with FSDP/HSDP is available as an experiment.
+- [2025/04] Training the diffusion model [FLUX](torchtitan/models/flux/) with FSDP/HSDP is available as an experiment.
 - [2025/04] The frontend implementation of [SimpleFSDP](torchtitan/experiments/simple_fsdp/), a compiler-based FSDP framework, is available as an experiment.
 - [2024/12] GPU MODE [lecture](https://www.youtube.com/watch?v=VYWRjcUqW6w) on torchtitan.
 - [2024/07] [Presentation](https://pytorch2024.sched.com/event/1fHn3) at PyTorch Conference 2024.