dev-libs/aws-c-event-stream: Fix dependencies (#695206)

dev-libs/aws-c-event-stream: Fix dependencies (#695206)

Unfortunately I forgot to add dev-libs/aws-checksums to the list of
dependencies.
This is explicitly not a revision bump, as this would cause rebuilds
for everybody who has already merged this successfully.

Bug: https://bugs.gentoo.org/695206
Closes: https://bugs.gentoo.org/695206
Package-Manager: Portage-2.3.76, Repoman-2.3.17
Signed-off-by: Sven Eden <yamakuzure@gmx.net>
Closes: https://github.com/gentoo/gentoo/pull/13045
Signed-off-by: Joonas Niilola <juippis@gentoo.org>