random: Correct wording in a comment

[markj]

Summary

In the calculation of the cutoff value, we haven't changed the window
size itself, just the example formula, which takes the window size as a
parameter.

[cem]

I'll take your word for it :)

[markj]

In D52002#1188010, @cem wrote:

I'll take your word for it :)

I could have at least provided some links:

• NIST 800-90B recommendations (see footnote 10 on page 35 of the PDF): https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-90B.pdf
• CRITBINOM documentation: https://support.microsoft.com/en-us/office/critbinom-function-207d5482-810f-49a2-a1a8-b2e7dac01096