fix(embedding-providers): use renamed --provider-api-key in update no-op error

`update`'s "provide at least one field" guard message still listed
`--api-key`, which was the original local flag name before it was renamed
to `--provider-api-key` to avoid colliding with the global Hotdata auth
flag. A user following the error guidance would reach for `--api-key`
(the global auth flag), not the provider key.

One-character class of fix; caught by the PR review bot on #67.

Author: anoop-narang

src/embedding_providers.rs

@@ -155,7 +155,7 @@ pub fn update(
     if name.is_none() && config.is_none() && api_key.is_none() && secret_name.is_none() {
         eprintln!(
             "{}",
-            "error: provide at least one of --name, --config, --api-key, --secret-name.".red()
+            "error: provide at least one of --name, --config, --provider-api-key, --secret-name.".red()
         );
         std::process::exit(1);
     }