Remove outdated comment in primality testing.

This comment dates to SSLeay. It appears to be describing the
incremental trial division strategy where they would pick a starting
candidate, compute moduli by small primes, and then update by
incrementing the candidate and saved moduli instead of dividing from
scratch. We use a simpler rejection sampling strategy.

Change-Id: If2203d616f2b1f632bcd7033ceb60a83d1b75674
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/48047
Reviewed-by: Adam Langley <agl@google.com>

crypto/fipsmodule/bn/prime.c

@@ -115,10 +115,6 @@
 #include "../../internal.h"
 
 
-// The quick sieve algorithm approach to weeding out primes is Philip
-// Zimmermann's, as implemented in PGP.  I have had a read of his comments and
-// implemented my own version.
-
 // kPrimes contains the first 1024 primes.
 static const uint16_t kPrimes[] = {
     2,    3,    5,    7,    11,   13,   17,   19,   23,   29,   31,   37,