Disable some more tests under CI

tmux-commandline can fail with

```
prompt 4>     commandline -i "echo $(printf %0"$COLUMNS"d)"
```

And I just can't even.

job_summary is annoyingly tight.

Also count cancel_event as a *skip*, not success.

tests/checks/tmux-commandline.fish

@@ -2,6 +2,8 @@
 #REQUIRES: command -v tmux
 # Somehow $LINES is borked on NetBSD?
 #REQUIRES: test $(uname) != NetBSD
+# Haunted under CI
+#REQUIRES: test -z "$CI"
 
 set -g isolated_tmux_fish_extra_args -C '
     bind ctrl-q "functions --erase fish_right_prompt" "commandline \'\'" clear-screen

tests/pexpects/cancel_event.py

@@ -21,7 +21,7 @@ if "CI" in os.environ:
     import sys
 
     print("SKIPPING cancel_event.py")
-    sys.exit(0)
+    sys.exit(127)
 
 # Verify that cancel-commandline does what we expect - see #7384.
 send("not executed")

tests/pexpects/job_summary.py

@@ -17,9 +17,9 @@ import os
 import signal
 import sys
 
-# Disable under SAN - keeps failing because the timing is too tight
-if "FISH_CI_SAN" in os.environ:
-    sys.exit(0)
+# Disable under CI - keeps failing because the timing is too tight
+if "CI" in os.environ:
+    sys.exit(127)
 
 # Test job summary for interactive shells.
 expect_prompt()