Fix message text for INCOMPATIBLE_ENUM_COMPARISON

^KT-28516 Fixed

idea/testData/diagnosticMessage/incompatibleEnums.kt

@@ -0,0 +1,22 @@
+// !DIAGNOSTICS_NUMBER: 2
+// !DIAGNOSTICS: INCOMPATIBLE_ENUM_COMPARISON
+// !MESSAGE_TYPE: TEXT
+
+enum class E1 {
+    A, B
+}
+
+enum class E2 {
+    A, B
+}
+
+fun foo1(e1: E1, e2: E2) {
+    e1 == e2
+}
+
+fun foo2(e1: E1, e2: E2) {
+    when (e1) {
+        E2.A -> {}
+        else -> {}
+    }
+}

idea/testData/diagnosticMessage/incompatibleEnums1.txt

@@ -0,0 +1,2 @@
+<!-- incompatibleEnums1 -->
+Comparison of incompatible enums 'E1' and 'E2' is always unsuccessful

idea/testData/diagnosticMessage/incompatibleEnums2.txt

@@ -0,0 +1,2 @@
+<!-- incompatibleEnums2 -->
+Comparison of incompatible enums 'E1' and 'E2' is always unsuccessful