[Buildroot] [PATCH] package/protobuf: update github url

[Peter Korsgaard]

>>>>> "Michael" == Michael Nosthoff via buildroot <buildroot at lists.buildroot.org> writes:

 > protobuf moved from the google org to protocolbuffers in 2018.
 > There is a redirect but we should use the official url.

 > Signed-off-by: Michael Nosthoff <buildroot at heine.tech>

Committed to 2021.02.x, 2021.05.x and 2021.08.x, thanks.

-- 
Bye, Peter Korsgaard