Set readOnlyRootFilesystem as true in Interceptor

[savitaashture]

Changes

As part of this PR #1735 handled only for Contorller and Webhook but not for interceptor
This PR will address that

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Release Notes

Interceptor Deployment security context `readOnlyRootFilesystem`  are set to true to increase the security and to avoid being flagged by the security scanner.

[khrm]

/lgtm
/approve

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[khrm]

/cherry-pick release-v0.29.x

[tekton-robot]

@khrm: once the present PR merges, I will cherry-pick it on top of release-v0.29.x in a new PR and assign it to you.

In response to this:

/cherry-pick release-v0.29.x

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[khrm]

/retest

[tekton-robot]

@khrm: new pull request created: #1763

In response to this:

/cherry-pick release-v0.29.x

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