Drop tvheadend from our repository
Due to the recent changes in OpenWrt:
- https://github.com/openwrt/packages/commit/326da3dbbc57b6c44bc0d0401529531c7d5dfb89#diff-1c715168bf7640e3599dc7e5f53a17d1d02113ee38fec52cef377c1d25b978cc
- https://github.com/openwrt/packages/commit/4a387bc568d25697c25575fdbd95d6d7d96bb9a8#diff-1c715168bf7640e3599dc7e5f53a17d1d02113ee38fec52cef377c1d25b978cc
We can drop tvheadend from our repository to use the upstream package.