Change docs links to actual file extension (.md)

See https://gerrit-review.googlesource.com/83950 for detailed context.

Change-Id: I61c3d092c3420d0bf8664fffccb4d6295881eaac
diff --git a/src/main/resources/Documentation/about.md b/src/main/resources/Documentation/about.md
index 1828d00..9816f36 100644
--- a/src/main/resources/Documentation/about.md
+++ b/src/main/resources/Documentation/about.md
@@ -8,4 +8,4 @@
 
 The maximum number of reviewers that are added as well as exceptions when no
 reviewers should be added by this plugin can be
-[configured per project](config.html).
+[configured per project](config.md).