docs(): update mac docs

docs/sources/installation/mac.md

@@ -11,28 +11,17 @@ Installation can be done using [homebrew](http://brew.sh/)
 Install latest stable:
 
 ```
-brew install grafana/grafana/grafana
-```
-
-To start grafana look at the command printed after the homebrew install completes.
-
-You can also add the grafana as tap.
-
-```
-brew tap grafana/grafana
+brew update
 brew install grafana
 ```
 
-Install latest unstable from master:
-
-```
-brew install --HEAD grafana/grafana/grafana
-```
+To start grafana look at the command printed after the homebrew install completes.
 
 To upgrade use the reinstall command
 
 ```
-brew reinstall --HEAD grafana/grafana/grafana
+brew update
+brew reinstall grafana
 ```