update send address for candidate withdrawal

[nathanclairmonte]

Rationale

TS have requested that careers@canonical.com be retired, and thus we need to update the send address used on canonical.com. The address they would like us to use instead is noreply+talent-mailbox@canonical.com.

Done

• Updated send address in site.yaml

Issue / Card

WD-16902

[webteam-app]

Demo

Jenkins

demos.haus