build(deps): relax torch floor to >=2.12

litert-torch 0.9.1 (latest on PyPI) requires torch<2.13.0, so a
torch>=2.13 floor is unresolvable in CI until litert-torch 0.10 is
published.

Author: pctablet505

requirements.txt

@@ -6,7 +6,7 @@ tensorflow-text>=2.20.1;platform_system != 'Windows'
 # Torch.
 --extra-index-url https://download.pytorch.org/whl/cpu
 litert-torch
-torch>=2.13
+torch>=2.12
 
 # Jax.
 jax[cpu]