Remove -index.md files from publishing (reduces OPS publishing errors)

[danieljurek]

Fixes: https://github.com/Azure/azure-sdk-for-js/issues/26493

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

Learn Build status updates of commit 8171dfb:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
docfx.json	:white_check_mark:Succeeded

For more details, please refer to the build report.

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