Update free_file_hosts.txt

[brycampbell]

Some abuse of free file sharing services mentioned here:

1. https://blog.google/threat-analysis-group/exposing-initial-access-broker-taies-conti/
2. https://attack.mitre.org/groups/G1011/

Human-Operated Phishing at scale evidence here adds in some confidence to the inclusion of both of these services. However, the misuse at this point is now 3 years ago, something to consider is the timing out of abused services when adding them.