Correct code block formatting in weightconverter.md

[zhulinchng]

Fix formatting of code block in weightconverter.md

What does this PR do?

Fixes code block formatting in weightconverter.md #44840

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[zhulinchng]

@stevhliu When reading the docs, I've found and fixed a typo in the documentation:

transformers/docs/source/en/weightconverter.md

Line 69 in 16a5b09

```x

[stevhliu]

good catch, thanks!

[HuggingFaceDocBuilderDev]

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