Stop building node@16 images for GitLab

https://gitlab.com/gitlab-org/gitlab/-/merge_requests/106898 got merged,
so we do not need to build the old versions for GitLab anymore.

.gitlab/ci/gitlab.images.yml

@@ -28,7 +28,7 @@ gitlab:
         POSTGRESQL: ['12', '13', '14', '15']
         GOLANG: ['1.19', '1.20']
         RUST: ['1.65']
-        NODE: ['16.14', '18.16']
+        NODE: ['18.16']
         CHROME: ['109', '113']
 
 # Used by GitLab's compile-production-assets and compile-test-assets jobs
@@ -47,7 +47,7 @@ gitlab-assets:
       - OS: ['debian:bullseye']
         RUBY: ['2.7', '3.0', '3.1', '3.2']
         GIT: ['2.33']
-        NODE: ['16.14', '18.16']
+        NODE: ['18.16']
 
 # Used by GitLab's Review app jobs
 gitlab-review-app: