github: Remove exclude for centos in nightly-ad-server jobs

With the ability to build and run ad-server images based on CentOS
using nightly builds of Samba, we could enable corresponding jobs
by removing the exclude for 'centos' from the matrix.

Signed-off-by: Anoop C S <[email protected]>

Author: anoopcs9

.github/workflows/container-image.yml

@@ -161,8 +161,6 @@ jobs:
       matrix:
         os: [centos, fedora]
         arch: [amd64]
-        exclude:
-          - os: centos
     env:
       BUILDAH_FORMAT: oci
     steps:
@@ -234,8 +232,6 @@ jobs:
       matrix:
         os: [centos, fedora]
         arch: [amd64]
-        exclude:
-          - os: centos
     needs:
       - build-nightly-server
       - build-nightly-ad-server