Update docs/docker/upgrading/v5-v6.md

Co-authored-by: RD WebDesign <github@rdwebdesign.com.br>
Signed-off-by: Adam Warner <github@adamwarner.co.uk>

docs/docker/upgrading/v5-v6.md

@@ -5,7 +5,7 @@
 
 ## Changed Environment Variables
 
-Nearly all environment variables from previous versions have been removed, but functionality can be replicated by setting their `FTLCONF_` equivalent instead. (See [Configuration](../configuration.md#ftlconf_setting) page for more details)
+Nearly all environment variables from previous versions have been removed, but functionality can be replicated by setting their `FTLCONF_` equivalent instead. (See [Configuration](../configuration.md#configuring-ftl-via-the-environment) page for more details)
 
 ### Misc