docs: updates links to windows beta build

docs/sources/installation/windows.md

@@ -14,7 +14,7 @@ weight = 3
 Description | Download
 ------------ | -------------
 Latest stable package for Windows | [grafana.4.0.2.windows-x64.zip](https://grafanarel.s3.amazonaws.com/builds/grafana-4.0.2.windows-x64.zip)
-Latest beta package for Windows | [grafana.4.1.0-beta1.windows-x64.zip](https://grafanarel.s3.amazonaws.com/builds/)
+Latest beta package for Windows | [grafana.4.1.0-beta1.windows-x64.zip](https://grafanarel.s3.amazonaws.com/builds/grafana-4.1.0-beta1.windows-x64.zip)
 
 ## Configure