Add "-i" to sendmail's pipe

[FedericoHeichou]

• Resolves: [Bug]: Double dots in links in emails #39594

Summary

Symfony Mailer replaces "\n." with "\n..".
If the email to be sent contains links when they are breaklined a line may start with a ., thus can generating a URL like https://www..example.com/[...] or https://www.example.com/index..php/[...] .
With "-i" this replacement is not performed.

TODO

• ...

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[FedericoHeichou]

Sorry, I created a new one. The Github's code is a mess and used the wrong email to perform the commit...
#39607