Plugins: Unsigned chromium file should not invalidate signature for Renderer plugin (#59104)

* Plugins: Unsigned chromium file should not invalidate signature for Renderer plugin

* fix test

* re-work solution

pkg/plugins/manager/testdata/renderer-added-file/plugin/plugin.json

@@ -0,0 +1,11 @@
+{
+  "type": "renderer",
+  "name": "Test",
+  "id": "test-renderer",
+  "backend": true,
+  "executable": "test",
+  "info": {
+    "version": "1.0.0",
+    "description": "Test"
+  }
+}