yq package is now provided in the BigBlueButton support PPA for BBB 2.5,
so we can depend on the package now. Ensure the dependency is specific
to avoid an incompatible yq version 4 from being installed.
beta.6 updates mediasoup 3.9.0 which has a new Meson build system
That new build system does a pretty good job cleaning compiler leftovers on its
own, so theoretically our cleanup code isn't needed anymore.
Amend history:
build/packages-template/bbb-webrtc-sfu/build.sh -> v2.6.0-beta.6 to beta.7
... drop build artifacts from compiling mediasoup. This reduces package
size from ~ 54 MB to ~ 12 MB.
Additionally this drops the `npm rebuild` command from the after-install
script. It should not be necessary to recompile stuff during
installation. To ensure a clean `node_modules` directory, it will be
cleaned in the before-install script.
