ci: run visual-regression "install node 24" step under bash

The mcr.microsoft.com/playwright:v1.59.1-noble container's default shell
is dash, which rejects `set -o pipefail`. Force bash for the one step
that needs it.

Author: FelixTJDietrich

.github/workflows/pr-health-checks.yml

@@ -188,6 +188,7 @@ jobs:
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
 
       - name: Install Node 24
+        shell: bash
         run: |
           set -euo pipefail
           curl -fsSL https://deb.nodesource.com/setup_24.x | bash -