docs: update _index.md to reflect config file name and location change (#13390)

Co-authored-by: J Stickler <julie.stickler@grafana.com>

docs/sources/setup/upgrade/_index.md

@@ -23,10 +23,10 @@ If possible try to stay current and do sequential updates. If you want to skip v
 Using docker you can check changes between 2 versions of Loki with a command like this:
 
 ```
-export OLD_LOKI=2.3.0
-export NEW_LOKI=2.4.1
-export CONFIG_FILE=loki-local-config.yaml
-diff --color=always --side-by-side <(docker run --rm -t -v "${PWD}":/config grafana/loki:${OLD_LOKI} -config.file=/config/${CONFIG_FILE} -print-config-stderr 2>&1 | sed '/Starting Loki/q' | tr -d '\r') <(docker run --rm -t -v "${PWD}":/config grafana/loki:${NEW_LOKI} -config.file=/config/${CONFIG_FILE} -print-config-stderr 2>&1 | sed '/Starting Loki/q' | tr -d '\r') | less -R
+export OLD_LOKI=2.9.4
+export NEW_LOKI=3.0.0
+export CONFIG_FILE=local-config.yaml
+diff --color=always --side-by-side <(docker run --rm -t -v "${PWD}":/config grafana/loki:${OLD_LOKI} -config.file=/etc/loki/${CONFIG_FILE} -print-config-stderr 2>&1 | sed '/Starting Loki/q' | tr -d '\r') <(docker run --rm -t -v "${PWD}":/config grafana/loki:${NEW_LOKI} -config.file=/etc/loki/${CONFIG_FILE} -print-config-stderr 2>&1 | sed '/Starting Loki/q' | tr -d '\r') | less -R
 ```
 
 The `tr -d '\r'` is likely not necessary for most people, seems like WSL2 was sneaking in some windows newline characters...