Update ote-events to sticky version

[hhkaos]

https://tools.opentechevents.org/embed/

Currently using

<script id="ote-events-widget" type="module" src="https://tools.opentechevents.org/embed/ote-events.js"></script>

Sticky version:

<script id="ote-events-widget" type="module" src="https://tools.opentechevents.org/embed/v0.3.0/ote-events.js"></script>

Or fixed to latest (it could break if spec changes)

<script id="ote-events-widget" type="module" src="https://tools.opentechevents.org/embed/latest/ote-events.js"></script>