Rewritten ChangeVariableMutabilityFix

#KT-7877 Fixed

idea/testData/quickfix/variables/changeMutability/localInGetter.kt

@@ -0,0 +1,8 @@
+// "Make variable mutable" "true"
+
+val String.prop: Int
+    get() {
+        val p = 1
+        <caret>p = 2
+        return p
+    }

idea/testData/quickfix/variables/changeMutability/localInGetter.kt.after

@@ -0,0 +1,8 @@
+// "Make variable mutable" "true"
+
+val String.prop: Int
+    get() {
+        var p = 1
+        <caret>p = 2
+        return p
+    }