[CI] Increase the gitian build timeout

Summary: This might be useful for the linux build when several dependencies need to be recompiled (it happened on my VM).

Test Plan:

./contrib/teamcity/build-configurations.py gitian-linux

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D14052