Java to Kotlin converter: declaring locals as var's in most of cases when needed, dropped forceLocalVariableImmutability setting

j2k/tests/testData/ast/nullability/VariableInitializedWithNull.kt

@@ -1,6 +1,6 @@
 // !specifyLocalVariableTypeByDefault: true
 fun foo(b: Boolean) {
-    val s: String? = null
+    var s: String? = null
     if (b) {
         s = "abc"
     }