Update Gerrit v3.2 release notes with ListGroups --query2 rename

The Change-Id: I1a1bdbbcd has renamed the --query2 option in the
ListGroup command into --query, which is classified as a breaking
change because it impacts the external API.

Bug: Issue 12858
Change-Id: I82e33ae94e31b97a98f6c1bf202d6c62684ec703
diff --git a/pages/site/releases/3.2.md b/pages/site/releases/3.2.md
index 369f6a5..d52aff3 100644
--- a/pages/site/releases/3.2.md
+++ b/pages/site/releases/3.2.md
@@ -108,6 +108,10 @@
 * [Issue 12527](https://bugs.chromium.org/p/gerrit/issues/detail?id=12527):
 Elasticsearch: Support for EOL versions v5.6 and v6.0 to v6.5 is discontinued
 
+* [Issue 12858](https://bugs.chromium.org/p/gerrit/issues/detail?id=12858):
+ListGroups: the --query2 option in the groups query REST-API has been renamed to
+--query
+
 ## New Features
 
 ### File Uploads