fix: allow unauthenticated signals connection to fix 401

the signals handles authentication itself in the middleware thus we
should allow unauthenticated requests to pass through

Signed-off-by: Heikki Hellgren <heikki.hellgren@op.fi>

.changeset/ninety-toys-bake.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-signals-backend': patch
+---
+
+Fix unauthorized signals connection by allowing unauthenticated requests

plugins/signals-backend/src/plugin.ts

@@ -58,7 +58,7 @@ export const signalsPlugin = createBackendPlugin({
           }),
         );
         httpRouter.addAuthPolicy({
-          path: '/health',
+          path: '*',
           allow: 'unauthenticated',
         });
       },