community/yt-dlp: use upstream release tarball for man page

Since we don't have pandoc in community/ the man page is otherwise not build and the -doc subpackage remains empty. The now used tarball contains a pre-built version of the man page and does thus not require pandoc:

>>> Size difference for yt-dlp-doc: 28 KiB -> 152 KiB
--- filelist-yt-dlp-doc-old	2021-11-21 19:27:31.725170152 +0100
+++ filelist-yt-dlp-doc	2021-11-21 19:27:31.735170323 +0100
@@ -3,5 +3,7 @@
 usr/share/
 usr/share/doc/
 usr/share/doc/yt_dlp/
+usr/share/doc/yt_dlp/README.txt
 usr/share/man/
 usr/share/man/man1/
+usr/share/man/man1/yt-dlp.1.gz