Reverted addition of env variable

Author: Felix Kleinekathöfer

.github/workflows/build.yml

@@ -127,7 +127,6 @@ jobs:
         build-args: |
           GITHUB_USER=${{ github.actor }}
           GITHUB_TOKEN=${{ github.token }}
-          GITHUB_REPO=https://github.com/SpongePowered/SpongeDocs
           CROWDIN_TOKEN=${{ secrets.CROWDIN_TOKEN }}
           CROWDIN_PROJECT_ID=${{ secrets.CROWDIN_PROJECT_ID }}
           BASE_URL=https://docs.spongepowered.org