base32: remove unnecessary "if" condition
base32: remove unnecessary "if" condition

This is a patch to apply the same change as CL 76610045.

LGTM=nigeltao
R=nigeltao
CC=golang-codereviews
https://codereview.appspot.com/77460044

Committer: Nigel Tao <58ae08b3356928ff9c67562b4719487d54fe8348@golang.org>

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