fixed changelog issue link

CHANGELOG.md

@@ -9,7 +9,7 @@
 - [Issue #660](https://github.com/grafana/grafana/issues/660). OpenTSDB: fix opentsdb queries that returned more than one series
 
 **Change**
-- [Issue #660](https://github.com/grafana/grafana/issues/660). Dashboard: The panel error bar has been replaced with a small error indicator, this indicator does not change panel height and is a lot less intrusive. Hover over it for short details, click on it for more details.
+- [Issue #681](https://github.com/grafana/grafana/issues/681). Dashboard: The panel error bar has been replaced with a small error indicator, this indicator does not change panel height and is a lot less intrusive. Hover over it for short details, click on it for more details.
 
 # 1.7.0-rc1 (2014-08-05)