Drop "Reflection types not loaded" diagnostic

Reflection types are now considered to be built-in, so their absence means the
runtime is broken and the compiler can't work at all; this condition probably
should be handled on another level for all built-in types

compiler/testData/diagnostics/tests/deprecated/functionUsage.kt

@@ -1,4 +1,4 @@
-// !DIAGNOSTICS: -UNUSED_EXPRESSION, -REFLECTION_TYPES_NOT_LOADED
+// !DIAGNOSTICS: -UNUSED_EXPRESSION
 
 class UsefulClass(val param: Int = 2) {
     fun get(instance: Any, property: PropertyMetadata) : Int = 1