fix(kernel/expr, kernel/level): if caching is enabled during finaliza…

…tion, these modules would register a finalizer after finalization of the main thread

The deleted lines were not really needed. They were added before we had
the thread finalization code.

src/kernel/expr.cpp

@@ -738,7 +738,6 @@ void initialize_expr() {
 }
 
 void finalize_expr() {
-    enable_expr_caching(false);
     delete g_Prop;
     delete g_Type1;
     delete g_dummy;

src/kernel/level.cpp

@@ -761,7 +761,6 @@ void initialize_level() {
 }
 
 void finalize_level() {
-    enable_level_caching(false);
     delete g_level_one;
     delete g_level_zero;
 }