Remove PWA screenshots from manifest config

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

config/packages/pwa.yaml

@@ -29,14 +29,6 @@ pwa:
               sizes: 192x192
               type: image/png
               purpose: maskable
-        screenshots:
-            - src: '%kernel.project_dir%/public/favicon.png'
-              label: E-Ticket - Accueil
-              format: png
-            - src: '%kernel.project_dir%/public/screen.png'
-              label: E-Ticket - Billetterie associative
-              form_factor: wide
-              format: png
         shortcuts:
             - name: Evenements
               short_name: Events