2.13: Add note about Maven Central's discontinuation of TLS v1.1

Bug: Issue 9330
Change-Id: I480c2d362619f6e864367964bfa80b560e4b619b
diff --git a/releases/2.13.md b/releases/2.13.md
index 165d916..e49aca7 100644
--- a/releases/2.13.md
+++ b/releases/2.13.md
@@ -47,6 +47,21 @@
   java -jar gerrit.war init -d site_path
 ```
 
+### HTTPS TLS1.1 support discontinued by Maven Central.
+
+As of June 18th 2018, Maven Central
+[discontinued support for TLS v1.1 and below](https://central.sonatype.org/articles/2018/May/04/discontinue-support-for-tlsv11-and-below/).
+
+When initializing a new site with Java 7, this causes download of third
+party dependencies such as the MySQL connector to fail. It is therefore
+necessary to explicitly enable TLS v1.2 on the invocation of java:
+
+``` sh
+  java -Dhttps.protocols=TLSv1.2 gerrit.war init -d site_path
+```
+
+This does not affect Java 8, which enables TLS v1.2 by default.
+
 ### Manual Schema Update for Reviewed Flags
 
 Sites that have already upgraded to version 2.13 may want to migrate from the