[frontend] increase the build timeout limit because of chromium
    
    Based on user feedback and calculation, something in range
    21h - 24h should be sufficiently long to build chromium.
    I am setting the timeout to 21 hours to see if it helps,
    but we may have to increase it again.
    
    This change was requested on mailing list:
    
        https://lists.fedorahosted.org/archives/list/copr-devel \\
        @lists.fedorahosted.org/thread/WQHLPI2ZV6RAJ5I4I4GW6FKU4LTSTX55/