Fix installation errors and the example for limited resources

[sherlcok314159]

📌 Checklist before creating the PR

• [x] I have created an issue for this PR for traceability
• [ ] The title follows the standard format: [doc/gemini/tensor/...]: A concise description
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🚨 Issue number

This should fix #4847 #2743 #3602 #3370 #2972

📝 What does this PR do?

• Improve installation documentation for apex which plays a role in Colossal-AI installation.
• Fix the gradient_accumulation error when using colossalai_gemini strategy in the limited resources.

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• [x] I have performed a self-review of my code
• [x] I have added thorough tests.
• [ ] I have added docstrings for all the functions/methods I implemented

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