revert: revert "fix: remove unneeded comparer on custom tags in filte…

…r expression"

My bad. it was not unneeded, but necessary.

This reverts commit 873f85b.

Shoko.Server/Filters/FilterExtensions.cs

@@ -54,7 +54,7 @@ public static Filterable ToFilterable(this SVR_AnimeSeries series)
             TagsDelegate = () =>
                 series.AniDB_Anime?.Tags.Select(a => a.TagName).ToHashSet() ?? [],
             CustomTagsDelegate = () =>
-                series.AniDB_Anime?.CustomTags.Select(a => a.TagName).ToHashSet() ?? [],
+                series.AniDB_Anime?.CustomTags.Select(a => a.TagName).ToHashSet(StringComparer.InvariantCultureIgnoreCase) ?? [],
             YearsDelegate = () =>
                 series.Years,
             SeasonsDelegate = () =>