*: 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/build/fietsje/proto/shelf.proto b/build/fietsje/proto/shelf.proto
index 394e5f0..52573a7 100644
--- a/build/fietsje/proto/shelf.proto
+++ b/build/fietsje/proto/shelf.proto
@@ -16,7 +16,7 @@
 
 syntax = "proto3";
 package nexantic.build.fietsje;
-option go_package = "git.monogon.dev/source/nexantic.git/build/fietsje/proto";
+option go_package = "source.monogon.dev/build/fietsje/proto";
 
 // The Shelf is a cache/lockfile of Fietsje dependencies. See //build/fietsje/shelf.go for more information.
 // This proto definition is used to generate text proto files. As such, repeated fields have singular names.