doc: updated RELEASES.md for #1398

RELEASES.md

@@ -319,6 +319,9 @@ The previous release of Trippy introduced a bug ([#1290](https://github.com/fuji
 caused reverse DNS lookups to be enqueued multiple times when the `dns-ttl` expired, potentially leading to the hostname
 being displayed as `Timeout: xxx` for a brief period.
 
+A long standing bug ([#1398](https://github.com/fujiapple852/trippy/issues/1398)) which caused the TUI sample history
+and frequency charts to ignore sub-millisecond samples has been fixed.
+
 This release fixes a bug ([#1287](https://github.com/fujiapple852/trippy/issues/1287)) that caused a tracer panic when
 parsing certain ICMP extensions with malformed lengths.