fix(doc): fix typo tekton -> openshift

[gregsheremeta]

Description of your changes:
fix typo (tekton -> openshift) in "Installing kfp-tekton on OpenShift Pipelines" section

Environment tested:
n/a

• Python Version (use python --version): n/a
• Tekton Version (use tkn version): n/a
• Kubernetes Version (use kubectl version): n/a
• OS (e.g. from /etc/os-release): n/a

Checklist:

• The title for your pull request (PR) should follow our title convention. Learn more about the pull request title convention used in this repository.

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[yhwang]

/lgtm

Thanks for the fix

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gregsheremeta, yhwang

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [yhwang]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[yhwang]

@gregsheremeta can you follow the link here: https://cla.developers.google.com/
to finish the CLA sign-up? you can see details from the failed job: cla/google.

[gregsheremeta]

can you follow the link here: https://cla.developers.google.com/
to finish the CLA sign-up?

✔️