Fix 'cta.archivefile.max_size_gb' calculation: power of 1000, not 1024

The configuration cta.archivefile.max_size_gb is currently converted to bytes using :

m_archiveFileMaxSize = archiveFileMaxSize.has_value() ?  static_cast<uint64_t>(archiveFileMaxSize.value()) * 1024 * 1024 * 1024 : 0;

This is wrong. The GB is a power of 1000, while GiB is the actual power of 1024.

Therefore, we should have:

m_archiveFileMaxSize = archiveFileMaxSize.has_value() ?  static_cast<uint64_t>(archiveFileMaxSize.value()) * 1000 * 1000 * 1000 : 0;