Fix the indexSync documentation

Document the default value of the indexSync.enabled option and move the
NOTE about indexSync feature close to the indexSync section
documentation.

Change-Id: I1211e62379ab3c69040a3603572aa9406a6a6964

src/main/resources/Documentation/config.md

diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
index 2bc9721..836d9f1 100644
--- a/src/main/resources/Documentation/config.md
+++ b/src/main/resources/Documentation/config.md
@@ -91,9 +91,6 @@
     When set to `jgroups` or `provided` then all `peerInfo.*` sections are
     unnecessary and ignored.
 
-**NOTE:** The indexSync feature exposes a REST endpoint that can be used to discover project names.
-Admins are advised to restrict access to the REST endpoints exposed by this plugin.
-
 **Note:** For projects and groups reindexing, [scheduled indexer](https://gerrit-review.googlesource.com/Documentation/config-gerrit.html#scheduledIndexer) can be enabled with specific configurations.
 Example configurations:
 
@@ -112,9 +109,13 @@
 Groups and projects may become outdated if indexing events are missed due to the node being down or
 some networking issues.
 
+**NOTE:** The indexSync feature exposes a REST endpoint that can be used to discover project names.
+Admins are advised to restrict access to the REST endpoints exposed by this plugin.
+
 ```indexSync.enabled```
 :   When indexSync is enabled, the primary servers will synchronize indexes with the intention to
     self-heal any missed reindexing event.
+    When not specified, the default is `false`.
 
 ```indexSync.delay```
 :   If enabled, index sync will start running after this initial delay.