Fix the path to grafana-webserver in the Debian install docs.

docs/sources/installation/debian.md

@@ -122,8 +122,8 @@ To configure Grafana add a configuration file named `custom.ini` to the
 `conf` folder and override any of the settings defined in
 `conf/defaults.ini`.
 
-Start Grafana by executing `./grafana-server web`. The `grafana-server` binary needs
-the working directory to be the root install directory (where the binary
-and the `public` folder is located).
+Start Grafana by executing `./bin/grafana-server web`. The `grafana-server`
+binary needs the working directory to be the root install directory (where the
+binary and the `public` folder is located).