Update dependency ffmpeg to v7.1 (mastodon#32239)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Dockerfile

@@ -214,7 +214,7 @@ FROM build AS ffmpeg
 
 # ffmpeg version to compile, change with [--build-arg FFMPEG_VERSION="7.0.x"]
 # renovate: datasource=repology depName=ffmpeg packageName=openpkg_current/ffmpeg
-ARG FFMPEG_VERSION=7.0.2
+ARG FFMPEG_VERSION=7.1
 # ffmpeg download URL, change with [--build-arg FFMPEG_URL="https://ffmpeg.org/releases"]
 ARG FFMPEG_URL=https://ffmpeg.org/releases