Merge branch 'update-prometheus-custom-var-docs' into 'master'

Fix dashboard templating custom variable typo

See merge request gitlab-org/gitlab!33873

doc/user/project/integrations/prometheus.md

@@ -812,7 +812,7 @@ templating:
 
 ###### Full syntax
 
-This example creates a variable called `variable1`, with a default value of `var1_option_2`.
+This example creates a variable called `variable1`, with a default value of `value_option_2`.
 The label for the text box on the UI will be the value of the `label` key.
 The dashboard UI will display a dropdown with `Option 1` and `Option 2`
 as the choices.