appveyor: disable bintray
appveyor: disable bintray

We gradually filled up the free allocation, and they don't provide any
method to delete the oldest automatically.  You literally have to sit
there deleting one artifact at a time (we create 7 per commit) using
their webui.  I'm not going to do that.

While it's full, appveyor builds will just break.

So disable it.
sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets