doc: list of primes contains a non-prime

[axw]

The language specification has a code example which says 9 is prime:

    // list of prime numbers
    primes := []int{2, 3, 5, 7, 9, 11, 13, 17, 19, 991}

I'd just fix it, but I have to request approval from work first.

[rsc]

Comment 1:

ha ha

Status changed to Started.

[rsc]

Comment 2:

This issue was closed by revision c739dd2.

Status changed to Fixed.

[ianlancetaylor]

Comment 3:

Issue #8830 has been merged into this issue.

[minux]

Comment 4:

note: 9 is still in the list, and it seems to be intended.
ref https://golang.org/cl/5634046/ and https://golang.org/cl/5630043