Freeze the cert-manager 1.15 docs

[wallrj]

Preview: https://deploy-preview-1577--cert-manager.netlify.app/v1.15-docs/

Following the instructions from the release process:

(final release only) Freeze the docs/ folder by creating a copy , removing the pages from that copy that don't make sense to be versioned, and updating the manifest.json file:

export RELEASE=1.15
cp -r content/docs content/v${RELEASE}-docs
rm -rf content/v${RELEASE}-docs/{installation/supported-releases,installation/upgrading,release-notes,contributing}
sed -i.bak "s|docs/|v${RELEASE}-docs/|g" content/v${RELEASE}-docs/manifest.json
cat content/v${RELEASE}-docs/manifest.json \
  | jq 'del(.. | select(.path? | select(.) | test(".*(installation/supported-releases.md|installation/upgrading|release-notes|contributing).*")))' \
  | jq 'del(.. | select(.routes? == []))' >/tmp/manifest \
     && mv /tmp/manifest content/v${RELEASE}-docs/manifest.json

[cert-manager-prow[bot]]

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