fix: release cheat sheet doc typos

[ngelman1]

Changes

updated a typo in release-cheat-sheet.md and in release-pipeline.yaml
OLD: "notag"
NEW: "notags" (plural)
the old "notag" is a typo that simply leads nowhere, as the path https://infra.tekton.dev/tekton-releases/chains/previous/v0.13.0/release.notag.yaml simply doesn't exist

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Release Notes

NONE

[enarha]

/ok-to-test

[anithapriyanatarajan]

/kind bug

[anithapriyanatarajan]

/approve

[anithapriyanatarajan]

/lgtm

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