test: give the org-alias case the one organisation it describes

It said "an instance with one organisation" while running against the two
the case before it installed. The alias is what it is about, so the count
never mattered to the assertion — but the description was wrong, and a
description that can drift is worth less than none.

beep boop

Author: khvn26

internal/cmd/testdata/script/organisation.txtar

@@ -8,6 +8,7 @@ cmp stdout expect-list
 # Given: an instance with one organisation
 # When: the command is spelled `org`
 # Then: it is an alias for organisation
+fake orgs Acme=3
 exec flagsmith org list
 stdout 'Acme'