bgpwtf/machines/modules: fix bird_exporter

v.1.2.5's hash broke, let's just swiftly ignore this and update to
1.2.6.

Change-Id: I19757abeb2f279be6f56ca429441503710ed433f
diff --git a/bgpwtf/machines/modules/prometheus.nix b/bgpwtf/machines/modules/prometheus.nix
index 704c257..1ebb435 100644
--- a/bgpwtf/machines/modules/prometheus.nix
+++ b/bgpwtf/machines/modules/prometheus.nix
@@ -10,15 +10,15 @@
 
   birdExporter = pkgs.buildGoModule rec {
     pname = "bird-exporter";
-    version = "1.2.5";
+    version = "1.2.6";
     src = pkgs.fetchFromGitHub {
       owner = "czerwonk";
       repo = "bird_exporter";
       rev = version;
-      sha256 = "1qrhncy1f119f5rfgn2d1l6nvapaqkld4zb9bxzdqmmw6kicc7bs";
+      sha256 = "1yqizzlvwyxlrd2priqd1jx9s87yvsypqkmk81dacm1ra4xrs0nd";
     };
 
-    vendorSha256 = null;
+    vendorSha256 = "0wczj3g0c917hwjkz23xg5blb4z5a04v3wbx6kg0wfyb09c9bwx3";
   };
 
 in {