Remove the redundant and poorly worded warning message.

Remove the redundant and poorly worded warning message.

The paragraph above already says, clearly and correctly, that
"However, being completely deterministic, it is not suitable for
all purposes, and is completely unsuitable for cryptographic purposes."

Also we should make any promises about SystemRandom or os.urandom()
being cryptographically secure (they may be, but be can't validate
that promise).  Further, those are actual random number generators
not psuedo-random number generators.