Revert "Fix MLIR Toy tutorial JIT example and add a test to cover it"

This reverts commit ae15b1e.

This commit caused failures on the mlir windows buildbot

Author: sstamenova

mlir/examples/toy/Ch6/toyc.cpp

@@ -240,7 +240,7 @@ int runJit(mlir::ModuleOp module) {
   auto &engine = maybeEngine.get();
 
   // Invoke the JIT-compiled function.
-  auto invocationResult = engine->invokePacked("main");
+  auto invocationResult = engine->invoke("main");
   if (invocationResult) {
     llvm::errs() << "JIT invocation failed\n";
     return -1;

mlir/examples/toy/Ch7/toyc.cpp

@@ -241,7 +241,7 @@ int runJit(mlir::ModuleOp module) {
   auto &engine = maybeEngine.get();
 
   // Invoke the JIT-compiled function.
-  auto invocationResult = engine->invokePacked("main");
+  auto invocationResult = engine->invoke("main");
   if (invocationResult) {
     llvm::errs() << "JIT invocation failed\n";
     return -1;