*: git.monogon.dev -> source.monogon.dev

This implements T882, setting our (virtual) GOPATH to source.monogon.dev
for this repository.

Test Plan: Refactor, CI only.

X-Origin-Diff: phab/D686
GitOrigin-RevId: c5e2309089948ffc3a98e68e2e0e1cbb157d3a36
diff --git a/metropolis/proto/internal/internal.proto b/metropolis/proto/internal/internal.proto
index e82fe96..33a7239 100644
--- a/metropolis/proto/internal/internal.proto
+++ b/metropolis/proto/internal/internal.proto
@@ -15,7 +15,7 @@
 // limitations under the License.
 
 syntax = "proto3";
-option go_package = "git.monogon.dev/source/nexantic.git/metropolis/proto/internal";
+option go_package = "source.monogon.dev/metropolis/proto/internal";
 package metropolis.proto.internal;
 
 // Node describes a single node's state in etcd