Remove out-of-date info from config documentation

The documentation warns about a bug in core Gerrit, that was already
fixed in 2.10 and is no longer a problem.  Remove it.

Change-Id: I4c908dfdfc08ec3ea9e71246dbaed53a12abb29a
diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
index a3de35b..376330a 100644
--- a/src/main/resources/Documentation/config.md
+++ b/src/main/resources/Documentation/config.md
@@ -8,11 +8,6 @@
 Other projects can then override the configuration in their own
 `reviewers.config` file.
 
-WARNING: Due to a bug in Gerrit core in all released versions, the config
-file must be called `reviewers` and not `reviewers.config`.  That bug was
-fixed in upcoming 2.10 release (not released yet). Note that after upgrade,
-the file must be renamed to `reviewers.config`.
-
 ```
   [filter "*"]
     reviewer = john.doe@example.com