Meta: Hardcode lowercase repository name for devcontainer

This should unbreak CI.

.devcontainer/optimized/.devcontainer.json

@@ -7,5 +7,5 @@
 // getting you into your development environment faster!
 {
     "name": "SerenityOS (Pre-Built Image)",
-    "image": "ghcr.io/SerenityOS/serenity-devcontainer:base"
+    "image": "ghcr.io/serenityos/serenity-devcontainer:base"
 }

.github/workflows/dev-container.yml

@@ -10,7 +10,6 @@ on:
     # https://crontab.guru/#0_0_*_*_1
     - cron:  '0 0 * * 1'
 
-
 permissions:
   contents: read
   # Push images to GHCR.
@@ -34,6 +33,6 @@ jobs:
       - name: Build Base Dev Container Image
         uses: devcontainers/ci@v0.3
         with:
-          imageName: ghcr.io/${{ github.repository_owner }}/serenity-devcontainer
+          imageName: ghcr.io/serenityos/serenity-devcontainer
           imageTag: base,latest
           push: always