test: retire npm-test-registry and whitepaper builder images

1. They have vulnerabilities that are non-trivial effort to fix.
2. We haven't used them in a while so it makes sense for them to retire.
3. We can put them back in action whenever they become needed again,
they'll always be available in the git commit log.
4. This saves on CI resources which is something we are short on and
constantly need to optimize further.

Signed-off-by: Peter Somogyvari <[email protected]>

.github/workflows/ci.yaml

@@ -2373,36 +2373,6 @@ jobs:
           ignore-unfixed: true
           vuln-type: 'os,library'
           severity: 'CRITICAL,HIGH'
-  ghcr-test-npm-registry:
-    runs-on: ubuntu-20.04
-    steps:
-      - uses: actions/[email protected]
-      - name: ghcr.io/hyperledger/cactus-test-npm-registry
-        run: DOCKER_BUILDKIT=1 docker build ./tools/docker/test-npm-registry/ -f ./tools/docker/test-npm-registry/Dockerfile -t cactus-test-npm-registry
-      - name: Run Trivy vulnerability scan for cactus-test-npm-registry
-        uses: aquasecurity/[email protected]
-        with:
-          image-ref: 'cactus-test-npm-registry'
-          format: 'table'
-          exit-code: '1'
-          ignore-unfixed: true
-          vuln-type: 'os,library'
-          severity: 'CRITICAL,HIGH'
-  ghcr-whitepaper:
-    runs-on: ubuntu-20.04
-    steps:
-      - uses: actions/[email protected]
-      - name: ghcr.io/hyperledger/cactus-whitepaper
-        run: DOCKER_BUILDKIT=1 docker build ./whitepaper/ -f ./whitepaper/Dockerfile -t cactus-whitepaper
-      - name: Run Trivy vulnerability scan for cactus-whitepaper
-        uses: aquasecurity/[email protected]
-        with:
-          image-ref: 'cactus-whitepaper'
-          format: 'table'
-          exit-code: '1'
-          ignore-unfixed: true
-          vuln-type: 'os,library'
-          severity: 'CRITICAL,HIGH'
 name: Cactus_CI
 'on':
   pull_request: