Fix incorrect error message

src/main/java/org/asamk/signal/App.java

@@ -292,7 +292,7 @@ public class App {
         } catch (IOException e) {
             throw new IOErrorException("Failed to load local accounts file", e);
         } catch (AccountCheckException e) {
-            throw new UnexpectedErrorException("Failed to load local accounts file", e);
+            throw new UnexpectedErrorException("Failed to load account file", e);
         }
     }