Update unstable VLCKit with latest libav optimizations

This speeds-up H264 decoding on ARM64 devices up to 10%

compileVLCforiOS.sh

@@ -14,7 +14,7 @@ SKIPLIBVLCCOMPILATION=no
 UNSTABLEVLCKIT=yes
 
 TESTEDVLCKITHASH=766c3b7fa
-TESTEDUNSTABLEVLCKITHASH=5c8c17632
+TESTEDUNSTABLEVLCKITHASH=5b4f892cf
 TESTEDMEDIALIBRARYKITHASH=e6b613478
 TESTEDQUINCYKITHASH=f1d93b96b