Improve provider docs

* Rephrase link from setup-provider to csaf_provider options.
* Remove a few superfluous whitespace chars.

docs/csaf_provider.md

@@ -30,8 +30,8 @@ Following options are supported in the config file:
  - provider_metadata.mirror_on_CSAF_aggregators: Mirror on aggregators
  - remote_validator: Use a remote validator service. Not used by default.
    `{ "url" = "http://localhost:3000", "presets" = ["mandatory"], "cache" = "/var/lib/csaf/validations.db" }`
- - provider_metadata.publisher: Set the publisher. Default:  
-```toml 
+ - provider_metadata.publisher: Set the publisher. Default:
+```toml
 [provider_metadata.publisher]
 category = "vendor"
 name = "Example Company"