K1: don't report assignment TYPE_MISMATCH in BI under feature ON

Related to KT-54004

compiler/testData/diagnostics/testsWithStdLib/builderInference/unsafeAssignment_noReport.kt

@@ -0,0 +1,21 @@
+// !LANGUAGE: +NoBuilderInferenceWithoutAnnotationRestriction
+
+class Foo<T : Any> {
+    fun doSmthng(arg: T) {}
+    var a: T? = null
+}
+
+fun <T : Any> myBuilder(block: Foo<T>.() -> Unit) : Foo<T> = Foo<T>().apply(block)
+
+fun main(arg: Any) {
+    val x = 57
+    val value = myBuilder {
+        doSmthng("one ")
+        a = 57
+        a = x
+        if (arg is String) {
+            a = arg
+        }
+    }
+    println(value.a?.count { it in 'l' .. 'q' })
+}