Java to Kotlin converter: replacing equals call to ==/!= and no redundant parethesis generation

#KT-4426 Fixed

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

@@ -1,7 +1,7 @@
 // !specifyLocalVariableTypeByDefault: true
 fun foo(b: Boolean) {
-    val s: String? = ((if (b)
+    val s: String? = (if (b)
         "abc"
     else
-        null))
+        null)
 }