Add Fabien to the keys for gitian signing
Summary: As per title
Test Plan:
./check-keys.sh
Ensure all the keys are already here or imported
Note: I cannot reach the current keyserver in check-keys.sh from my machine atm.
If the script fails for you, consider patching D2420 first.
Reviewers: #bitcoin_abc, deadalnix, jasonbcox
Reviewed By: #bitcoin_abc, deadalnix, jasonbcox
Subscribers: jasonbcox, teamcity, schancel
Differential Revision: https://reviews.bitcoinabc.org/D2421