Correct order for INFRA_IF_NAME in script

[tim-vk]

Changed the order, the line is now copy-past-able and works.

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[gemini-code-assist]

Code Review

This pull request corrects a command in the OpenThread Border Router Docker build guide. It ensures that the INFRA_IF_NAME environment variable is passed to the bash execution rather than the curl command, which correctly configures the setup script. There are no review comments, and the change is correct.