*: 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/pkg/supervisor/BUILD.bazel b/metropolis/pkg/supervisor/BUILD.bazel
index ac00fe7..2062522 100644
--- a/metropolis/pkg/supervisor/BUILD.bazel
+++ b/metropolis/pkg/supervisor/BUILD.bazel
@@ -9,7 +9,7 @@
         "supervisor_support.go",
         "supervisor_testhelpers.go",
     ],
-    importpath = "git.monogon.dev/source/nexantic.git/metropolis/pkg/supervisor",
+    importpath = "source.monogon.dev/metropolis/pkg/supervisor",
     visibility = ["//metropolis:__subpackages__"],
     deps = [
         "//metropolis/pkg/logtree:go_default_library",