FIR: add forgotten test data for old FE test

compiler/testData/diagnostics/tests/inference/nothingType/implicitInferenceTToFlexibleNothing.fir.kt

@@ -0,0 +1,11 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE -UNCHECKED_CAST -UNUSED_PARAMETER
+// !LANGUAGE: +NewInference
+// SKIP_TXT
+
+import java.util.*
+
+fun <T> foo (f: () -> List<T>): T = null as T
+
+fun main() {
+    val x = foo { Collections.emptyList() }
+}