Description of problem:

The config keys are always filtered out for the frontend plugins which reads configurations using ConfigApi even though the @visibility: frontend is defined in `config.d.ts` of those plugins.

Steps to Reproduce:

1. Add the configuration values in app-config.yaml
   example:

quay: 
 uiUrl: 'https://quay.io'

1. Run `yarn start` and navigate to the browser. In the console you can see the warnings.

Actual results:

Browser console warning

index.esm.js:388 Failed to read configuration value at 'quay.uiUrl' as it is not visible. See https://backstage.io/docs/conf/defining#visibility for instructions on how to make it visible.

Expected results:

Frontend plugins should be able to access the configuration values, if the visibility of the config is set to `frontend`.

Reproducibility (Always/Intermittent/Only Once):
Always

Additional info (Such as Logs, Screenshots, etc):

Backstage config Reader executes this block of code when the NODE_ENV is development - https://github.com/backstage/backstage/blob/master/packages/config/src/reader.ts#L265-L278 

slack thread - https://redhat-internal.slack.com/archives/C05HGAR2DT5/p1715165060479499