Relax restrictions on explicit versions (#660)

Instead of pinning specific versions for `fastapi` and `uvicorn`, only a
minimum version is set now instead.

Author: marbre

sharktank/requirements.txt

@@ -17,5 +17,5 @@ datasets
 torch>=2.3.0
 
 # Serving deps.
-fastapi==0.112.2
-uvicorn==0.30.6
+fastapi>=0.112.2
+uvicorn>=0.30.6