revert to stable web ui

the react-based ui is too slow for our needs, janky, the log viewer
doesn't work quite right (breaking after ~600 lines of logs viewed),
loses updates to sub-builds, and just blanks its entire screen when a
build finishes. the old ui doesn't do that.

buildbot_nix/__init__.py

@@ -862,7 +862,6 @@ class GerritNixConfigurator(ConfiguratorBase):
         config["secretsProviders"].append(systemd_secrets)
 
         config["www"].setdefault("plugins", {})
-        config["www"]["plugins"].update(dict(base_react={}))
 
         if "auth" not in config["www"]:
             config["www"]["auth"] = LixSystemsOAuth2('buildbot', read_secret_file('buildbot-oauth2-secret'), autologin=True)

nix/coordinator.nix

@@ -153,7 +153,7 @@ in
         ps.treq
         ps.psycopg2
         (ps.toPythonModule pkgs.buildbot-worker)
-        pkgs.buildbot-plugins.www-react
+        pkgs.buildbot-plugins.www
         (pkgs.python3.pkgs.callPackage ../default.nix { })
       ];
     };