Update Dockerfile

changed youtube_dl to yt-dlp and combined install line

Co-authored-by: Jouni Järvinen <rautamiekka@users.noreply.github.com>

Dockerfile

@@ -1,6 +1,5 @@
 FROM python:alpine
-RUN python3 -m pip install -U gallery-dl
-RUN python3 -m pip install -U youtube_dl
+RUN python3 -m pip install -U gallery-dl yt-dlp
 RUN apk update
 RUN apk add ffmpeg
 ENTRYPOINT [ "gallery-dl" ]