(#4994) Change log level to 'warn' and add more context around the error

Author: Akshay Dewan

plugin-infra/go-plugin-access/src/main/java/com/thoughtworks/go/plugin/access/common/settings/PluginSettingsMetadataLoader.java

@@ -61,8 +61,9 @@ void fetchPluginSettingsMetaData(GoPluginDescriptor pluginDescriptor) {
         List<ExtensionSettingsInfo> validMetadata = allSettingsAndViewPairsWhichAreValid(allMetadata);
 
         if (validMetadata.size() == 0) {
-            LOGGER.error("Failed to fetch plugin settings metadata for plugin {}. Maybe the plugin does not implement plugin settings and view?", pluginId);
-            LOGGER.error("Plugin: {} - Metadata load info: {}", pluginId, allMetadata);
+            LOGGER.warn("Failed to fetch plugin settings metadata for plugin {}. Maybe the plugin does not implement plugin settings and view?", pluginId);
+            LOGGER.warn("Plugin: {} - Metadata load info: {}", pluginId, allMetadata);
+            LOGGER.warn("Not all plugins are required to implement the request above. This error may be safe to ignore.");
             return;
         }