chore: clean some trivial code

[muchvo]

Description

1. Clean some trivial code
2. Update examples

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds core functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update in the documentation)

Implemented Tasks

• Subtask 1
• Subtask 2
• Subtask 3

Checklist

Go over all the following points, and put an x in all the boxes that apply.
If you are unsure about any of these, don't hesitate to ask. We are here to help!

• I have read the CONTRIBUTION guide. (required)
• My change requires a change to the documentation.
• I have updated the tests accordingly. (required for a bug fix or a new feature)
• I have updated the documentation accordingly.
• I have reformatted the code using make format. (required)
• I have checked the code using make lint. (required)
• I have ensured make test pass. (required)

[codecov-commenter]

Codecov Report

Merging #214 (ebd184e) into dev (b821adf) will decrease coverage by 0.03%.
The diff coverage is 32.00%.

❗ Current head ebd184e differs from pull request most recent head eb9bc0e. Consider uploading reports for the commit eb9bc0e to get more accurate results

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@@            Coverage Diff             @@
##              dev     #214      +/-   ##
==========================================
- Coverage   95.99%   95.96%   -0.03%     
==========================================
  Files         118      118              
  Lines        5987     5992       +5     
==========================================
+ Hits         5747     5750       +3     
- Misses        240      242       +2     

Impacted Files	Coverage Δ
omnisafe/common/statistics_tools.py	95.54% <0.00%> (-0.61%)	⬇️
omnisafe/utils/exp_grid_tools.py	50.00% <25.00%> (-41.67%)	⬇️
omnisafe/common/experiment_grid.py	96.43% <100.00%> (ø)
omnisafe/utils/command_app.py	84.21% <100.00%> (+9.60%)	⬆️

... and 2 files with indirect coverage changes

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[Gaiejj]

LGTM.

[zmsn-2077]

LGTM.