Fix ExitError() param type in reading-input-buffer-events.md

[Simran-B]

The declaration uses a constant string pointer but the definition had used a non-constant string pointer. The example only uses constant strings, so unifying the types to LPCSTR should be okay. Otherwise, both should be LPSTR to anticipate non-constant strings.

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

Learn Build status updates of commit 6e759f9:

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docs/reading-input-buffer-events.md	:white_check_mark:Succeeded	View

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