Remove matrix-widget-api as a dep & remove livekit stuff from widget init

We'll always have matrix-widget-api as a dep through js-sdk so also
specifyin it ourselves just means we'll end up using a different version
when the js-sdk upgrade their copy and get wierd errors. We could add a
peerDependency if we really felt the need?

package.json

@@ -58,7 +58,6 @@
     "livekit-client": "1.12.3",
     "lodash": "^4.17.21",
     "matrix-js-sdk": "github:matrix-org/matrix-js-sdk#0d46aeb5a4d44685885adc502f46688a4bed65b6",
-    "matrix-widget-api": "^1.3.1",
     "mermaid": "^8.13.8",
     "normalize.css": "^8.0.1",
     "pako": "^2.0.4",