Fix the history pager deletion test on macOS

It appears that the shift-delete key escape sequence is not being generated
because there's no mapping for it in screen-256color, causing the test to fail.
Switch to using f1 for the test.

tests/checks/tmux-history-search.fish

@@ -3,8 +3,11 @@
 # disable on github actions because it's flakey
 #REQUIRES: test -z "$CI"
 
+# The default history-pager-delete binding is shift-delete which
+# may not have a terminfo entry for screen-256color, so rebind to F1.
 set -g isolated_tmux_fish_extra_args -C '
     set -g fish_autosuggestion_enabled 0
+    bind -k f1 history-pager-delete or backward-delete-char
 '
 isolated-tmux-start
 
@@ -52,7 +55,7 @@ isolated-tmux send-keys C-e C-u C-r
 tmux-sleep
 isolated-tmux send-keys "echo sdifjsdoifjsdoifj"
 tmux-sleep
-isolated-tmux send-keys S-DC
+isolated-tmux send-keys F1
 isolated-tmux capture-pane -p | grep "(no matches)"
 # CHECK: (no matches)
 isolated-tmux send-keys Enter C-e C-u "echo foo" Enter