Put the reading from yaml back and add a logger warning per dmr's req…

…uest.

synapse/config/workers.py

@@ -155,6 +155,11 @@ def read_config(self, config: JsonDict, **kwargs: Any) -> None:
         self.worker_name = config.get("worker_name", self.worker_app)
         self.instance_name = self.worker_name or "master"
 
+        # FIXME: Remove this check after a suitable amount of time.
+        self.worker_main_http_uri = config.get("worker_main_http_uri", None)
+        if self.worker_main_http_uri is not None:
+            logger.warning("The config option worker_main_http_uri is unused since Synapse 1.72. It can be safely removed from your configuration.")
+
         # This option is really only here to support `--manhole` command line
         # argument.
         manhole = config.get("worker_manhole")