Fix inconsistent casing of 'site administrator'

[Sukhendu2002]

Trac ticket: https://core.trac.wordpress.org/ticket/48879

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This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

[github-actions]

A commit was made that fixes the Trac ticket referenced in the description of this pull request.

SVN changeset: 59800
GitHub commit: 9160fbd

This PR will be closed, but please confirm the accuracy of this and reopen if there is more work to be done.

[github-actions]

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