Clean Jersey 2.x method that is already implemented in 3.1

Signed-off-by: jansupol <[email protected]>

Author: jansupol

core-common/src/main/java/org/glassfish/jersey/internal/config/SystemPropertiesConfigurationModel.java

@@ -230,9 +230,4 @@ public Set<Class<?>> getClasses() {
     public Set<Object> getInstances() {
         return null;
     }
-
-    // Jersey 2.x
-    private boolean hasProperty(String name) {
-        return getProperty(name) != null;
-    }
 }