Remove cmake "test" target

This can no longer be overridden, which means we have a broken "test"
target now. Instead, you need to call "make fish_run_tests".

Blergh.

Fixes #11116

tests/checks/features-qmark1.fish

@@ -1,3 +1,2 @@
-# Explicitly overriding HOME/XDG_CONFIG_HOME is only required if not invoking via `make test`
 # RUN: %fish --features '' -c 'string match --quiet "??" ab ; echo "qmarkon: $status"'
 #CHECK: qmarkon: 1

tests/checks/symlinks-not-overwritten.fish

@@ -1,8 +1,5 @@
-# Explicitly overriding HOME/XDG_CONFIG_HOME is only required if not invoking via `make test`
 # RUN: fish=%fish %fish %s
 
-mkdir -p $XDG_CONFIG_HOME/fish
-
 # fish_variables
 set -l target_file $XDG_CONFIG_HOME/fish/target_fish_variables
 set -l fish_variables $XDG_CONFIG_HOME/fish/fish_variables