fix: off-by-one error in GpuSelector.get_gpu_arg

gpu <= len(self._valid_gpus) should be gpu < len(self._valid_gpus).

The list is zero-indexed, so requesting gpu index equal to the list
length causes an IndexError. For example, with 2 valid GPUs (indices
0 and 1), requesting gpu=2 passes the check (2 <= 2) but
self._valid_gpus[2] is out of bounds.

frigate/ffmpeg_presets.py

@@ -63,7 +63,7 @@ class LibvaGpuSelector:
         if not self._valid_gpus:
             return ""
 
-        if gpu <= len(self._valid_gpus):
+        if gpu < len(self._valid_gpus):
             return self._valid_gpus[gpu]
         else:
             logger.warning(f"Invalid GPU index {gpu}, using first valid GPU")