MFH: r465566 by cmt

update thunderbird to 52.7.0

Release Notes: https://www.mozilla.org/en-US/thunderbird/52.7.0/releasenotes/

PR: 226892
Approved by: jbeich (maintainer)
Security: c71cdc95-3c18-45b7-866a-af28b59aabb5
Approved by: ports-secteam blanket