fix(framepack): remove broken torchvision.io.video monkey-patch

torchvision 0.26 removed the torchvision.io.video submodule entirely
(only image I/O remains). The monkey-patch in install_requirements
(`torchvision.io.video.av = av`) was attempting to swap PyAV into a
torchvision-internal that no longer exists, raising AttributeError on
every FramePack run. The patch is fully vestigial against modern
torchvision; PyAV is still installed by `install('av')`, and the
sdnext save path uses PyAV directly via av.open().

modules/framepack/framepack_install.py

@@ -18,9 +18,6 @@ def rename(src:str, dst:str):
 
 def install_requirements(attention:str='SDPA'):
     install('av')
-    import av
-    import torchvision
-    torchvision.io.video.av = av
     if attention == 'Xformers':
         log.debug('FramePack install: xformers')
         install('xformers')