Docs: fix config file info in upgrade guide (#83273)

* Updated incorrect custom config file names and locations

* Corrected default config file name

* Updated more config file info

* Apply suggestions from code review

Co-authored-by: Pepe Cano <825430+ppcano@users.noreply.github.com>

* Reverted change

* Fixed default config file info, added second custom file option, and added note about file locations

* Added file path for second custom option

* Apply suggestion from review

Co-authored-by: Usman Ahmad <usman.ahmad@grafana.com>

* Apply suggestion from review

Co-authored-by: Usman Ahmad <usman.ahmad@grafana.com>

* Apply suggestions from review

Co-authored-by: Usman Ahmad <usman.ahmad@grafana.com>

* Apply suggestion from review

* Add version interpolation syntax

* Updated wording

* Ran prettier

---------

Co-authored-by: Pepe Cano <825430+ppcano@users.noreply.github.com>
Co-authored-by: Usman Ahmad <usman.ahmad@grafana.com>

docs/sources/shared/back-up/back-up-grafana.md

@@ -17,8 +17,10 @@ Copy Grafana configuration files that you might have modified in your Grafana de
 
 The Grafana configuration files are located in the following directories:
 
-- Default configuration: `$WORKING_DIR/conf/defaults.ini`
-- Custom configuration: `$WORKING_DIR/conf/custom.ini`
+- Default configuration: `$WORKING_DIR/defaults.ini` (Don't change this file)
+- Custom configuration: `$WORKING_DIR/custom.ini`
+
+For more information on where to find configuration files, refer to [Configuration file location](https://grafana.com/docs/grafana/<GRAFANA_VERSION>/setup-grafana/configure-grafana/#configuration-file-location).
 
 {{% admonition type="note" %}}
 If you installed Grafana using the `deb` or `rpm` packages, then your configuration file is located at