fix(infra): lob-backtest-sweep secretName git-ssh-key -> argo-git-ssh-key

Matches the alpha-perception-template (which is the known-good
template in this namespace). Without the fix, ensure-binary +
run-cell + aggregate pods all stayed Init for ~20m with
'MountVolume.SetUp failed for volume "git-ssh-key" : secret
"git-ssh-key" not found' before the workflow timed out.

The actual secret in the foxhunt namespace is named
'argo-git-ssh-key' (see kubectl get secrets -n foxhunt). Same
template misconfig as the training-data PVC name.

infra/k8s/argo/lob-backtest-sweep-template.yaml

@@ -94,7 +94,7 @@ spec:
         claimName: training-data-pvc
     - name: git-ssh-key
       secret:
-        secretName: git-ssh-key
+        secretName: argo-git-ssh-key
         defaultMode: 0400
     - name: cargo-target-cuda
       persistentVolumeClaim: