Added quickfix for REDUNDANT_NULLABLE.

idea/testData/quickfix/nullables/afterRemoveRedundantNullable.kt

@@ -0,0 +1,4 @@
+// "Remove redundant '?'" "true"
+fun main(args : Array<String>) {
+    val x : Int? = 15
+}

idea/testData/quickfix/nullables/beforeRemoveRedundantNullable.kt

@@ -0,0 +1,4 @@
+// "Remove redundant '?'" "true"
+fun main(args : Array<String>) {
+    val x : Int??<caret> = 15
+}