buildroot

python-msgpack: remove useless 'depends on' in comment

In commit 6709fad224692ae5e0788bbd30145f7d622b52a4, python-msgpack was
bumped to a new version that has support for Python 3. The "depends on
BR2_PACKAGE_PYTHON' was removed for the main python-msgpack Config.in
option, but not from the comment. This commit fixes this
inconsistency.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>