internal: fix some typos
internal: fix some typos

Change-Id: I961a35e2f7a612f5837c1270a9eed773c0c178dc
GitHub-Last-Rev: d8e4ea4ea50f8c58dd2efde669e3059b7a382cd8
GitHub-Pull-Request: golang/dl#8
Reviewed-on: https://go-review.googlesource.com/c/dl/+/429017
Run-TryBot: Bryan Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
Reviewed-by: Michael Knyszek <4473450dc5c88f06e1fb787f303d7805ec2aee65@google.com>
Auto-Submit: Bryan Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
Reviewed-by: Bryan Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

golang/dl