Remove Task from the inner-most Import method in RealmArchiveModelImporter

One of my pending work items for post-realm merge.

The lowest-level import task is no longer asynchronous, as we don't want
it to span multiple threads to allow easier interaction with realm.
Removing the `Task` spec simplifies a heap of usages.

Individual usages should decide whether they want to run the import
asynchronously, by either using an alternative override or spooling up a
thread themselves.

osu.Game.Tests/Visual/Navigation/TestScenePresentScore.cs

@@ -4,7 +4,6 @@
 using System;
 using System.Linq;
 using NUnit.Framework;
-using osu.Framework.Extensions;
 using osu.Framework.Screens;
 using osu.Framework.Testing;
 using osu.Game.Beatmaps;
@@ -60,7 +59,7 @@ namespace osu.Game.Tests.Visual.Navigation
                             Ruleset = new OsuRuleset().RulesetInfo
                         },
                     }
-                }).GetResultSafely()?.Value;
+                })?.Value;
             });
         }
 
@@ -135,7 +134,7 @@ namespace osu.Game.Tests.Visual.Navigation
                     BeatmapInfo = beatmap.Beatmaps.First(),
                     Ruleset = ruleset ?? new OsuRuleset().RulesetInfo,
                     User = new GuestUser(),
-                }).GetResultSafely().Value;
+                }).Value;
             });
 
             AddAssert($"import {i} succeeded", () => imported != null);