[Pipelines] Revert disabling default caching flag and env var doc

[DharmitD]

Reverts https://github.com/kubeflow/website/pull/3880 and https://github.com/kubeflow/website/pull/3881 Reverting the two commits related to disabling default caching flag and env var docs, as the updates haven't been pushed out in the form of a Pipelines release yet. The updates have only been merged into kubeflow/pipelines repo's master, and hence it's best to not mention them in docs here yet, to avoid confusion and discrepancy.

Ref: https://github.com/kubeflow/pipelines/pull/11222

[gregsheremeta]

/lgtm

[jgarciao]

/lgtm

[google-oss-prow[bot]]

@jgarciao: changing LGTM is restricted to collaborators

In response to [this](https://github.com/kubeflow/website/pull/3898#issuecomment-2405513645): >/lgtm Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.

[google-oss-prow[bot]]

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