szurubooru: wrap szuru-admin with the required ffmpeg version (#469517)

pkgs/servers/web-apps/szurubooru/server.nix

@@ -5,6 +5,7 @@
   nixosTests,
   fetchPypi,
   python3,
+  ffmpeg_4-full,
 }:
 
 let
@@ -68,6 +69,10 @@ python.pkgs.buildPythonApplication {
     yt-dlp
   ];
 
+  makeWrapperArgs = [
+    "--prefix PATH : ${lib.makeBinPath [ ffmpeg_4-full ]}"
+  ];
+
   postInstall = ''
     mkdir $out/bin
     install -m0755 $src/szuru-admin $out/bin/szuru-admin