More parallel (#1215)

src/Universalis.DbAccess/MarketBoard/HistoryDbAccess.cs

@@ -114,6 +114,7 @@ public async Task<History> Retrieve(HistoryQuery query, CancellationToken cancel
                     LastUploadTimeUnixMilliseconds = new DateTimeOffset(mi.LastUploadTime).ToUnixTimeMilliseconds(),
                     Sales = marketSales
                         .AsParallel() // Iterating over the sales retrieved by the DataStax driver is synchronous, so we parallelize it
+                        .WithExecutionMode(ParallelExecutionMode.ForceParallelism)
                         .ToList(),
                 };
             });