ExternalData: Drop 'not security software' disclaimer (#15060)

Let clients do their own research on the current strength of each
hash algorithm to choose what is best for their needs.

Suggested-by: Nico Schlömer <nico.schloemer@gmail.com>
Merge topic 'ExternalData-drop-security-disclaimer' into next

f2ccc14b ExternalData: Drop 'not security software' disclaimer (#15060)