sha3: fix typo in comment
sha3: fix typo in comment

Change-Id: I2cd8fe55a3918771744ca6b53b8335282b7d2b40
GitHub-Last-Rev: 34bf09adb28954bbaa9db081379b3ff869fe7f28
GitHub-Pull-Request: golang/crypto#189
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/333429
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Trust: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@golang.org>

golang/crypto,golang/crypto,golang/crypto