Update codeowners on livekit branch (#3567)

Author: SimonBrandner

.github/CODEOWNERS

@@ -1,6 +1 @@
-*                         @matrix-org/element-web
-/.github/workflows/**     @matrix-org/element-web-app-team
-/package.json             @matrix-org/element-web-app-team
-/yarn.lock                @matrix-org/element-web-app-team
-/src/webrtc               @matrix-org/element-call-reviewers
-/spec/*/webrtc            @matrix-org/element-call-reviewers
+* @matrix-org/element-call-reviewers