Cannot clear file upload in Config tab of Kotsadm

[nabt]

Need the ability to clear an uploaded file from the Config tab via UI. Currently, the only way to fully clear a file from the Config is to use kubectl kots download/upload to change the value of the ConfigOption in the upstream/userdata/config.yaml by hand. We use file uploads to allow optional uploading of files, and have cases where the files are no longer needed in a customer environment, but can cause issues if still loaded in the configuration.