Chore: Fixed a spurious CI failure

Source/DafnyCore/Options/OptionRegistry.cs

@@ -1,6 +1,7 @@
 #nullable enable
 
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.CommandLine;
 using System.Linq;
@@ -30,8 +31,8 @@ public static void CheckOptionsAreKnown(IEnumerable<Option> allOptions) {
   // Note that legacy CLI options are not as cleanly enumerated and therefore
   // more difficult to completely categorize, which is the main reason the LibraryBackend
   // is restricted to only the new CLI.
-  private static readonly Dictionary<Option, GlobalOptionCheck> GlobalOptionChecks = new();
-  private static readonly Dictionary<Option, OptionScope> OptionScopes = new();
+  private static readonly ConcurrentDictionary<Option, GlobalOptionCheck> GlobalOptionChecks = new();
+  private static readonly ConcurrentDictionary<Option, OptionScope> OptionScopes = new();
 
   public static IEnumerable<Option> GlobalOptions => GlobalOptionChecks.Keys;
   public static IEnumerable<Option> TranslationOptions => OptionScopes.Where(kv => kv.Value == OptionScope.Translation).Select(kv => kv.Key);