*: 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/BUILD.bazel b/build/fietsje/proto/BUILD.bazel
index 816164b..833f8e4 100644
--- a/build/fietsje/proto/BUILD.bazel
+++ b/build/fietsje/proto/BUILD.bazel
@@ -10,7 +10,7 @@
 
 go_proto_library(
     name = "proto_go_proto",
-    importpath = "git.monogon.dev/source/nexantic.git/build/fietsje/proto",
+    importpath = "source.monogon.dev/build/fietsje/proto",
     proto = ":proto_proto",
     visibility = ["//visibility:public"],
 )
@@ -18,6 +18,6 @@
 go_library(
     name = "go_default_library",
     embed = [":proto_go_proto"],
-    importpath = "git.monogon.dev/source/nexantic.git/build/fietsje/proto",
+    importpath = "source.monogon.dev/build/fietsje/proto",
     visibility = ["//visibility:public"],
 )