Update 3.3 release notes

Add the introduction of config.openFiles setting to the release notes

Change-Id: I9970a1d6684eab184d991c632c920535714fd0a1
diff --git a/pages/site/releases/3.3.md b/pages/site/releases/3.3.md
index 633da4c..49b4ed1 100644
--- a/pages/site/releases/3.3.md
+++ b/pages/site/releases/3.3.md
@@ -72,6 +72,19 @@
 
 * Reply dialog posts patchset level comments instead of change messages.
 
+* [Issue 13670](https://bugs.chromium.org/p/gerrit/issues/detail?id=13670);
+  Introduce cache.openFiles setting in gerrit.config.
+
+  Persistent caches might require the allocation of additional file
+  descriptors depending on their configuration and backend engine.
+  This new setting allows the gerrit.sh to be aware of that and increase the
+  number of files accordingly before starting Gerrit.
+
+  E.g. when swapping the default H2 persistent cache implementation with the
+  [chronicle-map implementation](https://gerrit.googlesource.com/modules/cache-chroniclemap/+/refs/heads/stable-3.3)
+  the number of open files needs raising, since the latter is bound to open more
+  file descriptors, mostly due to its usage of memory mapped files.
+
 ### REST API changes
 
 * Reject REST requests with invalid enum values as bad request