/usr/share/phpbb3/www/language/en_us/email/group_request.txt is in phpbb3-l10n 3.0.10-4+deb7u3.
This file is owned by root:root, with mode 0o644.
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1 2 3 4 5 6 7 8 9 10 | Subject: A request to join your group has been made
Dear {USERNAME},
The user "{REQUEST_USERNAME}" has requested to join the group "{GROUP_NAME}" you moderate on "{SITENAME}".
To approve or deny this request for group membership please visit the following link:
{U_PENDING}
{EMAIL_SIG}
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