ci: sandbox is not a supported option

The Jenkins Jobs Builder files reference 'sandbox: true' as an option,
but this does not exist (anymore). Having the option causes warnings in
the Jenkins WebUI for admin users.

Signed-off-by: Niels de Vos <ndevos@redhat.com>

jobs/ci-job-validation.yaml

@@ -2,7 +2,6 @@
 - job:
     name: ci-job-validation
     project-type: pipeline
-    sandbox: true
     concurrent: true
     properties:
       - github:

jobs/commitlint.yaml

@@ -4,7 +4,6 @@
     description: Allow re-running commitlint tests, in case the commitlint app
       does not work correctly.
     project-type: pipeline
-    sandbox: true
     concurrent: true
     properties:
       - github:

jobs/containerized-tests.yaml

@@ -2,7 +2,6 @@
 - job:
     name: containerized-tests
     project-type: pipeline
-    sandbox: true
     concurrent: true
     properties:
       - github:

jobs/jjb-deploy.yaml

@@ -2,7 +2,6 @@
 - job:
     name: jjb-deploy
     project-type: pipeline
-    sandbox: true
     concurrent: false
     properties:
       - github:

jobs/jjb-validate.yaml

@@ -2,7 +2,6 @@
 - job:
     name: jjb-validate
     project-type: pipeline
-    sandbox: true
     concurrent: true
     properties:
       - github:

jobs/mini-e2e.yaml

@@ -11,7 +11,6 @@
 - job-template:
     name: 'mini-e2e_k8s-{k8s_version}'
     project-type: pipeline
-    sandbox: true
     concurrent: true
     properties:
       - github:
@@ -51,7 +50,6 @@
 - job-template:
     name: 'mini-e2e-helm_k8s-{k8s_version}'
     project-type: pipeline
-    sandbox: true
     concurrent: true
     properties:
       - github:

jobs/upgrade-tests.yaml

@@ -11,7 +11,6 @@
 - job-template:
     name: 'upgrade-tests-{test_type}'
     project-type: pipeline
-    sandbox: true
     concurrent: true
     properties:
       - github: