Fix libav version

Author: martenrichter

package-lock.json

@@ -38,7 +38,7 @@
     "jshashes": "^1.0.8",
     "jwt-decode": "^3.1.2",
     "katex": "^0.16.21",
-    "libav.js": "^4.8.6",
+    "libav.js": "=4.8.6",
     "libavjs-webcodecs-polyfill": "^0.4.4",
     "pdfjs-dist": "^4.2.67",
     "pica": "^7.1.0",