Fixing dead code in table_properties_collector_test

Summary:
There was a bug in table_properties_collector_test that this patch
is fixing: `!backward_mode && !test_int_tbl_prop_collector` in
TestCustomizedTablePropertiesCollector was never true, so the code
in the if-block never got executed. The reason is that the
CustomizedTablePropertiesCollector test was skipping tests with
`!backward_mode_ && !encode_as_internal`. The reason for skipping
the tests is unknown.

Test Plan: make table_properties_collector_test && ./table_properties_collector_test

Reviewers: rven, igor, yhchiang, anthony, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D43281

db/table_properties_collector_test.cc

@@ -365,10 +365,6 @@ TEST_P(TablePropertiesTest, CustomizedTablePropertiesCollector) {
   // Test properties collectors with internal keys or regular keys
   // for block based table
   for (bool encode_as_internal : { true, false }) {
-    if (!backward_mode_ && !encode_as_internal) {
-      continue;
-    }
-
     Options options;
     BlockBasedTableOptions table_options;
     table_options.flush_block_policy_factory =