Java: Don't offer "Unwrap 'else' branch" intention if it might cause unreachable code (IDEA-165428)

java/java-tests/testData/codeInsight/unwrapElseBranch/afterSimple3.java

@@ -0,0 +1,11 @@
+// "Unwrap 'else' branch" "true"
+
+class T {
+    String f(boolean b) {
+        if (b)
+            return "When true";
+            // Before
+        return "Otherwise";
+        // After
+    }
+}