downloads/faq: remove blockchain.raw

[plowsof]

current version on getmonero as of making this issue: (its has been updated since)

71697681675 Feb 23 2023 blockchain.new

benefits of this PR:

• reduction in resources for getmoneros server (bandwidth/disk usage)
• make people verify their own blockchain / decentralisation / reduced liability for getmonero , or any other buzzwords that may support this
• often times users run into problems when beginning with an imported blockchain or it simply prolonged their suffering before seeking help