[Wasm] Fix type parameters with external upper-bounds.

`klass.isExternal` was never reachable for type parameters
because of klass != null check

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/ir2wasm/TypeTransformer.kt

@@ -96,12 +96,12 @@ class WasmTypeTransformer(
                 error("Void type can't be used as a value")
 
             else -> {
-                val klass = this.getClass()
+                val klass = this.erasedUpperBound ?: builtIns.anyClass.owner
                 val ic = context.backendContext.inlineClassesUtils.getInlinedClass(this)
 
-                if (klass != null && klass.isExternal) {
+                if (klass.isExternal) {
                     WasmAnyRef
-                } else if (klass != null && isBuiltInWasmRefType(this)) {
+                } else if (isBuiltInWasmRefType(this)) {
                     when (val name = klass.name.identifier) {
                         "anyref" -> WasmAnyRef
                         "eqref" -> WasmEqRef