correctly implement JetSimpleNameReference.getTextRange() so that it doesn't include the @ character for references in labels

#KT-7560 Fixed

idea/testData/refactoring/rename/inplace/LabelFromFunction.kt

@@ -0,0 +1,5 @@
+fun xyzzy(): Any {
+    fun b<caret>ar(): Int {
+        return@bar 1
+    }
+}

idea/testData/refactoring/rename/inplace/LabelFromFunction.kt.after

@@ -0,0 +1,5 @@
+fun xyzzy(): Any {
+    fun foo(): Int {
+        return@foo 1
+    }
+}