Docs: Improve doc note about configuration from brew (#32659)

* Improve doc note about configuration from brew

When installed from homebrew, custom.ini isn't read. Instead, the
grafana.ini file used by the brew service[1] will need to be edited
directly.

[1] 9520636eb9/Formula/grafana.rb (L54)

* Update docs/sources/administration/configuration.md

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>
Co-authored-by: achatterjee-grafana <aparajita.chatterjee@grafana.com>

docs/sources/administration/configuration.md

@@ -36,7 +36,7 @@ Refer to [Configure a Grafana Docker image]({{< relref "configure-docker.md" >}}
 
 ### macOS
 
-By default, the configuration file is located at `/usr/local/etc/grafana/grafana.ini`. To configure Grafana, add a configuration file named `custom.ini` to the `conf` folder to override any of the settings defined in `conf/defaults.ini`.
+By default, the configuration file is located at `/usr/local/etc/grafana/grafana.ini`. For a Grafana instance installed using Homebrew, edit the `grafana.ini` file directly. Otherwise, add a configuration file named `custom.ini` to the `conf` folder to override any of the settings defined in `conf/defaults.ini`.
 
 ## Comments in .ini Files