Only when keyword should be highlighted in WhenWithOnlyElseInspection

#KT-31673 Fixed

idea/testData/inspectionsLocal/whenWithOnlyElse/subjectVariable/singleElse/noReference.kt

@@ -1,7 +1,7 @@
 fun test() {
-    when (val a = create()) {
+    when<caret> (val a = create()) {
         else -> use("")
-    }<caret>
+    }
 }
 
 fun create(): String = ""