HBASE-28621 Fixed comment: use before/after

For reverse scans, smaller/bigger is not accurate. Use before/after instead.

Author: PDavid

hbase-client/src/main/java/org/apache/hadoop/hbase/filter/PrefixFilter.java

@@ -76,9 +76,9 @@ public boolean filterRowKey(Cell firstRowCell) {
     if (filterAllRemaining()) {
       return true;
     }
-    // if the cell is smaller => return false so that getNextCellHint() is invoked.
+    // if the cell is before => return false so that getNextCellHint() is invoked.
     // if they are equal, return false => pass row
-    // if the cell is bigger => return true, filter row
+    // if the cell is after => return true, filter row
     // if we are passed the prefix, set flag
     int cmp;
     if (firstRowCell instanceof ByteBufferExtendedCell) {