java completion: don't deselect TreeMap (IDEA-189544)

it wasn't preselected because there were 8 signatures "to implement",
coming from Map default methods

java/java-tests/testData/codeInsight/completion/smartType/PreselectTreeMapWhenSortedMapExpected.java

@@ -0,0 +1,7 @@
+import java.util.*;
+
+class F {
+  {
+    SortedMap<String, String> m = new <caret>
+  }
+}