Don't send gitea status update when build is started

This was the source of a flaky test because sometimes hydra-notify was
quick enough to send out `buildStarted` and sometimes it apparently
wasn't which was quickly spottable with `nix build --rebuild`.

Removing that status update doesn't make a difference functionally,
gitea doesn't differentiate between "queued" and "running", so we send
the same status ("pending") out on both events, so we'd even safe one
avoidable request.

(cherry picked from commit 806c375c33)

flake.nix

@@ -348,10 +348,9 @@
 
                 response = json.loads(data)
 
-                assert len(response) == 3, "Expected exactly three status updates for latest commit (queued, started, finished)!"
+                assert len(response) == 2, "Expected exactly three status updates for latest commit (queued, finished)!"
                 assert response[0]['status'] == "success", "Expected finished status to be success!"
-                assert response[1]['status'] == "pending", "Expected started status to be pending!"
-                assert response[2]['status'] == "pending", "Expected queued status to be pending!"
+                assert response[1]['status'] == "pending", "Expected queued status to be pending!"
 
                 machine.shutdown()
               '';

src/lib/Hydra/Plugin/GiteaStatus.pm

@@ -88,10 +88,6 @@ sub buildQueued {
     common(@_, [], 0);
 }
 
-sub buildStarted {
-    common(@_, [], 1);
-}
-
 sub buildFinished {
     common(@_, 2);
 }