Disable getApproximateSizes test (#5035)

Summary:
Disabling `org.rocksdb.RocksDBTest.getApproximateSizes` test as it is frequently crashing on travis (#5020). It will be re-enabled once the root-cause is found and fixed.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5035

Differential Revision: D14294736

Pulled By: sagar0

fbshipit-source-id: e28bff0d143a58ad6c82991fec3d4cf8c0209995

java/src/test/java/org/rocksdb/RocksDBTest.java

@@ -1056,6 +1056,7 @@ public class RocksDBTest {
     }
   }
 
+  @Ignore("This test crashes. Re-enable after fixing.")
   @Test
   public void getApproximateSizes() throws RocksDBException {
     final byte key1[] = "key1".getBytes(UTF_8);