Remove pinned spaces==0.48.2 causing a hard build failure

Switching Space Hardware to ZeroGPU triggered a build failure:
"Cannot install spaces==0.48.2 and spaces==0.50.4 because these package
versions have conflicting dependencies." HF's build pipeline injects its
own required `spaces` version directly on the pip install command line
(spaces==0.50.4 currently) — our own explicit pin collided with it and
made the install unsatisfiable outright, regardless of which hardware
tier was selected (the build log showed the same conflict even after
reverting back to cpu-upgrade).

This is very likely also the actual root cause of today's "no real GPU
access" finding (torch.cuda.is_available() came back False from inside
an actual @spaces.GPU call) — spaces==0.48.2 is old enough that it may
never have correctly supported the current ZeroGPU allocation protocol.

Removing our own pin lets the platform's injected version win with no
conflict, on any hardware tier.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

requirements.txt

@@ -12,7 +12,6 @@ soundfile==0.12.1
 timm==1.0.12
 transformers==4.47.0
 omegaconf
-spaces==0.48.2
 gradio==5.25.0
 pydantic==2.8.2
 av