Add SecurityContext to Eventlistener containers under el-security-context flag

[savitaashture]

Changes

As part of this PR #1494 we introduced SecurityContext for Eventlistener containers
But for Openshift its not working so adding condition check to set SecurityContext for Eventlistener containers
Reason:
On Openshift cluster when we install Triggers EL container failed to start with below error

message: >-
        pods "el-listener-embed-binding-7b6bc5d595-" is forbidden: unable to
        validate against any security context constraint: [provider "anyuid":
        Forbidden: not usable by user or serviceaccount,
        pod.metadata.annotations[container.seccomp.security.alpha.kubernetes.io/event-listener]:
        Forbidden: seccomp may not be set,
        spec.containers[0].securityContext.runAsUser: Invalid value: 65532: must
        be in the ranges: [1001190000, 1001199999], provider "restricted":
        Forbidden: not usable by user or serviceaccount, provider "nonroot-v2":
        Forbidden: not usable by user or serviceaccount, provider "nonroot":
        Forbidden: not usable by user or serviceaccount, provider
        "hostmount-anyuid": Forbidden: not usable by user or serviceaccount,
        provider "machine-api-termination-handler": Forbidden: not usable by
        user or serviceaccount, provider "hostnetwork-v2": Forbidden: not usable
        by user or serviceaccount, provider "hostnetwork": Forbidden: not usable
        by user or serviceaccount, provider "hostaccess": Forbidden: not usable
        by user or serviceaccount, provider "node-exporter": Forbidden: not
        usable by user or serviceaccount, provider "privileged": Forbidden: not
        usable by user or serviceaccount] 

It doesn't allow to set that's why added SecurityContext to Eventlistener containers under el-security-context flag which is True by default so it won't create any issue for K8S

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Release Notes

[savitaashture]

We also need this for 0.23.x

[savitaashture]

/retest

[khrm]

Do we need to add any tests? Otherwise, it looks fine.

/approve

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: khrm

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[khrm]

/kind bug

[khrm]

/kind cleanup

[savitaashture]

/test pull-tekton-triggers-integration-tests

[dibyom]

/lgtm