MapConverter: drop String map test, covered by StringMapConverter.

Author: greenrobot-team

tests/objectbox-java-test/src/test/java/io/objectbox/converter/FlexMapConverterTest.java

@@ -16,21 +16,6 @@
 
 public class FlexMapConverterTest {
 
-    @Test
-    public void keysString_valsString_works() {
-        FlexMapConverter converter = new StringFlexMapConverter();
-        Map<String, String> map = new HashMap<>();
-
-        convertAndBackThenAssert(null, converter);
-
-        convertAndBackThenAssert(map, converter);
-
-        map.put("Hello", "Grüezi");
-        map.put("💡", "Idea");
-        map.put("", "Empty String Key");
-        convertAndBackThenAssert(map, converter);
-    }
-
     @Test
     public void keysString_valsSupportedTypes_works() {
         FlexMapConverter converter = new StringFlexMapConverter();