Remove Antithesis docker build workflow (#4642)

## Issue Addressed

This PR remove Antithesis docker build CI workflow. Confirmed with Antithesis team that this is no longer used.

.github/workflows/docker-antithesis.yml

@@ -1,35 +0,0 @@
-name: docker antithesis
-
-on:
-    push:
-        branches:
-            - unstable
-
-concurrency:
-    group: ${{ github.workflow }}-${{ github.ref }}
-    cancel-in-progress: true
-
-env:
-    ANTITHESIS_PASSWORD: ${{ secrets.ANTITHESIS_PASSWORD }}
-    ANTITHESIS_USERNAME: ${{ secrets.ANTITHESIS_USERNAME }}
-    ANTITHESIS_SERVER: ${{ secrets.ANTITHESIS_SERVER }}
-    REPOSITORY: ${{ secrets.ANTITHESIS_REPOSITORY }}
-    IMAGE_NAME: lighthouse
-    TAG: libvoidstar
-
-jobs:
-    build-docker:
-        runs-on: ubuntu-22.04
-        steps:
-            - uses: actions/checkout@v3
-            - name: Update Rust
-              run: rustup update stable
-            - name: Dockerhub login
-              run: |
-                  echo "${ANTITHESIS_PASSWORD}" | docker login --username ${ANTITHESIS_USERNAME} https://${ANTITHESIS_SERVER} --password-stdin
-            - name: Build AMD64 dockerfile (with push)
-              run: |
-                  docker build \
-                      --tag ${ANTITHESIS_SERVER}/${REPOSITORY}/${IMAGE_NAME}:${TAG} \
-                      --file ./testing/antithesis/Dockerfile.libvoidstar .
-                  docker push ${ANTITHESIS_SERVER}/${REPOSITORY}/${IMAGE_NAME}:${TAG}