Add `ENABLE_SSH_LOG` to debugging problems (#19316)

- Add this option to the debugging problems section. So users that are
trying to debug SSH-related problems will get the errors logged from `cmd/serv.go`

docs/content/doc/advanced/logging-documentation.en-us.md

@@ -287,6 +287,7 @@ MODE = console
 LEVEL = debug ; please set the level to debug when we are debugging a problem
 ROUTER = console
 COLORIZE = false ; this can be true if you can strip out the ansi coloring
+ENABLE_SSH_LOG = true ; shows logs related to git over SSH.
 ```
 
 Sometimes it will be helpful get some specific `TRACE` level logging restricted