*: bump protobuf/protoc

This gets rid of the following spurious warnings when building
metropolis/proto:

    metropolis/proto/api/aaa.proto: warning: Import metropolis/proto/ext/authorization.proto but not used.
    metropolis/proto/api/management.proto: warning: Import metropolis/proto/ext/authorization.proto but not used.

Change-Id: Id61a058977e969ccabd2ebccfee53f3268dcf177
Reviewed-on: https://review.monogon.dev/c/monogon/+/312
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
diff --git a/WORKSPACE b/WORKSPACE
index 1e2d57b..5bd45f7 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -84,9 +84,9 @@
 
 http_archive(
     name = "com_google_protobuf",
-    sha256 = "758249b537abba2f21ebc2d02555bf080917f0f2f88f4cbe2903e0e28c4187ed",
-    strip_prefix = "protobuf-3.10.0",
-    urls = ["https://github.com/protocolbuffers/protobuf/archive/v3.10.0.tar.gz"],
+    sha256 = "c6003e1d2e7fefa78a3039f19f383b4f3a61e81be8c19356f85b6461998ad3db",
+    strip_prefix = "protobuf-3.17.3",
+    urls = ["https://github.com/protocolbuffers/protobuf/archive/v3.17.3.tar.gz"],
 )
 
 load("@com_google_protobuf//:protobuf_deps.bzl", "protobuf_deps")