*: 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/test/ktest/main.go b/metropolis/test/ktest/main.go
index 7f750b8..17a9f71 100644
--- a/metropolis/test/ktest/main.go
+++ b/metropolis/test/ktest/main.go
@@ -26,7 +26,7 @@
 	"os"
 	"time"
 
-	"git.monogon.dev/source/nexantic.git/metropolis/test/launch"
+	"source.monogon.dev/metropolis/test/launch"
 )
 
 var (