fix: remove orphaned new_unconfigured test helper

Missed in 3520dc7 — the #[cfg(test)] helper had no remaining callers
after the test revert, causing tarpaulin to fail with dead_code.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: pythoninthegrass

crates/mt-tauri/src/lastfm/client.rs

@@ -24,19 +24,6 @@ impl LastFmClient {
         }
     }
 
-    #[cfg(test)]
-    pub(crate) fn new_unconfigured() -> Self {
-        Self {
-            config: ApiKeyConfig {
-                api_key: None,
-                api_secret: None,
-            },
-            rate_limiter: Arc::new(RateLimiter::new()),
-            http_client: reqwest::Client::new(),
-            base_url: "https://ws.audioscrobbler.com/2.0/".to_string(),
-        }
-    }
-
     /// Check if API is properly configured
     pub(crate) fn is_configured(&self) -> bool {
         self.config.is_configured()