Meta: Hardcode lowercase repository name for devcontainer

This should unbreak CI.

.github/workflows/dev-container.yml

@@ -1,6 +1,6 @@
 # This workflow builds a docker image with the Dev Container CLI (https://github.com/devcontainers/cli)
-# 
-name: 'Build Dev Container Image' 
+#
+name: 'Build Dev Container Image'
 on:
   workflow_dispatch:
   push:
@@ -9,7 +9,6 @@ on:
   schedule:
     # https://crontab.guru/#0_0_*_*_1
     - cron:  '0 0 * * 1'
-  
 
 permissions:
   contents: read
@@ -25,7 +24,7 @@ jobs:
         uses: actions/checkout@v3
 
       - name: Login to GitHub Container Registry
-        uses: docker/login-action@v2 
+        uses: docker/login-action@v2
         with:
           registry: ghcr.io
           username: ${{ github.repository_owner }}
@@ -34,6 +33,6 @@ jobs:
       - name: Build Base Dev Container Image
         uses: devcontainers/ci@v0.3
         with:
-          imageName: ghcr.io/${{ github.repository_owner }}/serenity-devcontainer
+          imageName: ghcr.io/serenityos/serenity-devcontainer
           imageTag: base,latest
           push: always