Remove last trace of legacy oldestIndexedBlockTimestamp

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

@@ -189,7 +189,7 @@ export class ApiService {
   getHistoricalBlockFeeRates$(interval: string | undefined) : Observable<any> {
     return this.httpClient.get<any[]>(
       this.apiBaseUrl + this.apiBasePath + `/api/v1/mining/blocks/fee-rates` +
-      (interval !== undefined ? `/${interval}` : '')
+      (interval !== undefined ? `/${interval}` : ''), { observe: 'response' }
     );
   }