Fixed a missing uppercase letter in SpanOwner<T>

[Sergio0694]

Follow up for #301

What changes to the docs does this PR provide?

This fixes the title in the tab title in internet browsers.

PR Checklist

Please check if your PR fulfills the following requirements:

• Correctly picked the right branch to base the change off (master for new features, live for typos/improvements)
• For new pages, used the provided template
• For new features, added an entry in the Table of Contents
• Ran against a spell and grammar checker
• Contains NO breaking changes

[opbld31]

Docs Build status updates of commit 808afd2:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/high-performance/SpanOwner.md	✅Succeeded	View

For more details, please refer to the build report.

Note: Broken links written as relative paths are included in the above build report. For broken links written as absolute paths or external URLs, see the broken link report.

For any questions, please:

• Try searching in the Docs contributor and Admin Guide
• See the frequently asked questions
• Post your question in the Docs support channel

[opbld31]

Docs Build status updates of commit 808afd2:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/high-performance/SpanOwner.md	✅Succeeded	View

For more details, please refer to the build report.

Note: Broken links written as relative paths are included in the above build report. For broken links written as absolute paths or external URLs, see the broken link report.

For any questions, please:

• Try searching in the Docs contributor and Admin Guide
• See the frequently asked questions
• Post your question in the Docs support channel