Update alphagov/govuk-infrastructure digest to 3403b78

Author: govuk-ci

.github/workflows/actionlint.yml

@@ -13,4 +13,4 @@ jobs:
       - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10   # v6.0.3
         with:
           show-progress: false
-      - uses: alphagov/govuk-infrastructure/.github/actions/actionlint@b6e3293ee4405b58975b7e9d0257a8f15470013d # main
+      - uses: alphagov/govuk-infrastructure/.github/actions/actionlint@3403b78896dc3cbf7fb6b1c050b8ab34ade13624 # main