Fix year 2017->2018 on the speakers page

Change-Id: I7747305c835ecd31e6c1bdc26181c4a382207f40

speakers.md

diff --git a/speakers.md b/speakers.md
index 5f0fdd5..63f1a84 100644
--- a/speakers.md
+++ b/speakers.md
@@ -1,4 +1,4 @@
-# Gerrit User Summit 2017 - Speakers
+# Gerrit User Summit 2018 - Speakers
 
 ### Dave Borowitz - Google {#dborowitz}