[BUG] Asks for "To" even if "To" already specified in letter

Hi. I found a bug. Steps to reproduce:
- Create file /tmp/m with following text:
===
Subject: subj
To: example@example.com

text
===
- Send it using command "git send-email /tmp/m"

You will see that git asks for "To". git says: "To whom should the emails be sent (if anyone)?" I don't like this. git should just use "To" from /tmp/m without asking.

Seen with git 2.43.0.

If I execute "git send-email --to-cmd='#' /tmp/m" or "git send-email --to-cmd=':' /tmp/m" or "git send-email --to-cmd='true' /tmp/m", then "To" is not asked.

Same happens when I send one single patch without cover letter. Steps
to reproduce:
- Clone some repo
- Make some (single) commit
- Execute in the repo "git send-email --annotate HEAD^"
- Editor will be spawned. Add header "To: example@example.com", then
save and exit from the editor

You will see the question "To whom should the emails be sent (if anyone)?", too. And again you can workaround using --to-cmd tricks.