gnu: jami: Always remove contrib tarballs from the sources of Jami.

gnu: jami: Always remove contrib tarballs from the sources of Jami.

The origin used as the "sfl-patches" input contained bundled library tarballs,
and weighed 217 MiB.  After this change, it weighs 3.3 MiB.

* gnu/packages/jami.scm (jami-source): Rename #:without-daemon to
\#:keep-contrib-patches.  Delete the daemon/contrib/tarballs sub-directory even
when keeping the patches.  Delete extraneous code.
(%sfl-patches, %jami-sources): New variables.
(pjproject-jami, ffmpeg-jami, libring): Adjust to use the above variables.