docs(README_Zh): remove mentions of SquareLine Studio

[lhdjply]

Description of the feature or fix

Related #5638
docs(README_Zh): remove mentions of SquareLine Studio.

Notes

• Update the Documentation if needed.
• Add Examples if relevant.
• Add Tests if applicable.
• If you added new options to lv_conf_template.h run lv_conf_internal_gen.py and update Kconfig.
• Run scripts/code-format.py (astyle needs to be installed) and follow the Code Conventions
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• When changes were requested, re-request review to notify the maintainers.
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[kisvegabor]

Ah, thank you! I don't know what would I do without your all-seeing-eyes 😊