/api/v1/mining/difficulty/{interval} is not used

frontend/src/app/services/api.service.ts

@@ -154,13 +154,6 @@ export class ApiService {
     );
   }
 
-  getHistoricalDifficulty$(interval: string | undefined): Observable<any> {
-    return this.httpClient.get<any[]>(
-        this.apiBaseUrl + this.apiBasePath + `/api/v1/mining/difficulty` +
-        (interval !== undefined ? `/${interval}` : '')
-      );
-  }
-
   getHistoricalHashrate$(interval: string | undefined): Observable<any> {
     return this.httpClient.get<any[]>(
         this.apiBaseUrl + this.apiBasePath + `/api/v1/mining/hashrate` +