[doc] fix: fix typo in install

[angine04]

Fixes typo: Magetron to Megatron

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[gemini-code-assist]

Code Review

This pull request corrects a typo in the installation documentation, specifically changing "Magetron" to "Megatron" in the description of the nvidia-cudnn-cu12 package. I have no feedback to provide as the change is accurate and straightforward.