feat(ssrc-rewriting): Enable it by default.

Enable ssrc-rewriting by default, it can still be overwritten via config.js

modules/flags/FeatureFlags.js

@@ -15,7 +15,7 @@ class FeatureFlags {
      */
     init(flags) {
         this._runInLiteMode = Boolean(flags.runInLiteMode);
-        this._ssrcRewriting = Boolean(flags.ssrcRewritingEnabled);
+        this._ssrcRewriting = flags.ssrcRewritingEnabled ?? true;
         this._joinAsVisitor = Boolean(flags.enableJoinAsVisitor ?? true);
     }