Capitalize Error Boundaries in docs

[Dextheking1]

Addresses the Error Boundaries item in #6713.

What I did

Swept all docs pages (src/content/, excluding blog/ and community/) for prose occurrences of "error boundary"/"error boundaries" and capitalized them where they refer to the React Error Boundary concept, following the style guide in the issue.

The docs were already almost fully capitalized here: every other prose occurrence already read "Error Boundary"/"Error Boundaries". This PR fixes the two remaining spots, both in the componentDidCatch reference (src/content/reference/react/Component.md):

• "Error boundaries do not catch errors for:" → "Error Boundaries do not catch errors for:"
• "Errors thrown in the error boundary itself" → "Errors thrown in the Error Boundary itself"

What I deliberately left alone

• URL fragments and {/* */} heading anchor comments (e.g. #catching-rendering-errors-with-an-error-boundary) — changing those would break links
• The error-boundaries lint rule name in the ESLint plugin reference (rule identifier)
• Bare "boundary"/"boundaries" occurrences, which in context refer to Suspense boundaries or are generic usage

[github-actions]

Size changes

Details

📦 Next.js Bundle Analysis for react-dev

This analysis was generated by the Next.js Bundle Analysis action. 🤖

This PR introduced no changes to the JavaScript bundle! 🙌