Ext: Update to SVT-AV1 v0.9.1

ext/svt.cmd

diff --git a/ext/svt.cmd b/ext/svt.cmd
index 03485b8..2de8fa9 100755
--- a/ext/svt.cmd
+++ b/ext/svt.cmd
@@ -11,7 +11,7 @@
 : # If you're running this on Windows, be sure you've already run this (from your VC2019 install dir):
 : #    "C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\VC\Auxiliary\Build\vcvars64.bat"
 
-git clone -b v0.9.0 --depth 1 https://gitlab.com/AOMediaCodec/SVT-AV1.git
+git clone -b v0.9.1 --depth 1 https://gitlab.com/AOMediaCodec/SVT-AV1.git
 
 cd SVT-AV1
 cd Build/windows