RelNotes: name the release properly

In the title, we should state for which version this release notes document is about. Signed-off-by: Junio C Hamano <gitster@pobox.com>

Junio C Hamano committed Nov 19, 2018 at 08:23 UTC 0e94dab5be2fd17cfba634f8a29ba5461d2cbd9e
1 file changed +2 -2
Documentation/RelNotes/2.20.0.txt
+2 -2
@@ -1,5 +1,5 @@
1 -Git Release Notes
2 -=================
1 +Git 2.20 Release Notes
2 +======================
3
4 Backward Compatibility Notes
5 ----------------------------