docs(plugin-calendar): the "ObjectCalendar Component" heading and its intro paragraph are duplicated back-to-back

[yinlianghui]

Observation-class, tripped over while sweeping content/docs/plugins/plugin-calendar.mdx for colorMapping mentions during #4454 / #4493 (PR #4516). Cosmetic only — nothing renders wrong, the page just says the same thing twice — so this carries finding and no pm:queue. Not fixed in that PR because it is outside the dispatched surface.

What is duplicated

content/docs/plugins/plugin-calendar.mdx, immediately after the "CalendarView Schema API" block:

## ObjectCalendar Component

Calendar component designed for use with ObjectQL data sources.

## ObjectCalendar Component

Calendar component designed for use with ObjectQL data sources.

### Features
...

Two identical h2 headings and two identical intro sentences, back to back, with no content between them. The ### Features list that follows belongs to the section and is not duplicated — only the heading + intro pair is.

Why it matters at all

Low severity, but two concrete effects:

1. The docs site builds a table of contents from headings, so "ObjectCalendar Component" appears twice in the page nav, and the first entry links to an anchor with no content under it.
2. Duplicate heading text produces duplicate slug anchors (#objectcalendar-component and a de-duplicated variant), so a deep link to the section is ambiguous and can land on the empty one.

Fix shape

Delete the first heading + sentence pair. Single-file, single-hunk docs change; no code, no changeset needed beyond the repo's usual docs-only handling.

Note for whoever picks it up: content/docs/releases/ is never editable in a code PR, but the rest of content/docs/ is fine — this file is in the editable part.

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