Add support for case function (#4147)

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

src/Runner.Worker/ActionManifestManagerLegacy.cs

@@ -315,6 +315,7 @@ namespace GitHub.Runner.Worker
                     maxBytes: 10 * 1024 * 1024),
                 Schema = _actionManifestSchema,
                 TraceWriter = executionContext.ToTemplateTraceWriter(),
+                AllowCaseFunction = false,
             };
 
             // Expression values from execution context