Quick fix to spell check headers and tutorial

[learn-build-service-prod[bot]]

Learn Build status updates of commit 3c1a81a:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
bing-docs/bing-spell-check/reference/headers.md	:white_check_mark:Succeeded	View
bing-docs/bing-spell-check/tutorial/spellcheck.md	:white_check_mark:Succeeded	View

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