[branch-2.4] Restore method removed by HBASE-25277 to LP(CONFIG) coprocessors

-  @Override
-  public boolean postScannerFilterRow(final ObserverContext<RegionCoprocessorEnvironment> e,
-      final InternalScanner s, final Cell curRowCell, final boolean hasMore) throws IOException {
-    // 'default' in RegionObserver might do unnecessary copy for Off heap backed Cells.
-    return hasMore;
-  }