ripgrep-all: use ffmpeg 4
ripgrep-all: use ffmpeg 4

See also #120705. `ffmpeg` is only used to search for metadata and
chapters in video files (such as `.mkv`, `.mp4` etc.). Confirmed that
with both `ffmpeg` versions the same result is provided.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs