* proto: correct classification of authz token
The target authorization token had the invalid classification
"private". Fortunately, classification is a fail-closed system,
so this won't have exposed users authorization tokens, but
we should still use the correct classification. Use "secret".
* scripts: add Go script to remove gotags comments
The new version of grpc-gateway includes our gotags
comments in the generate swagger documentation. This
script removes all mentions of these.
* Upgrade grpc-gateway dependency
Mainly we need this to fix generation of our docs side API docs,
but it also includes a nice fix for the new Download RPC, i.e. it
now contains the correct response schema (a binary stream).