Update Level Up docs

[JihwanEom]

Summary

• Align command expression to command
• Fix typos

How to test

Checklist

• I have added unit tests to cover my changes.​
• I have added integration tests to cover my changes.​
• I have added the description of my changes into CHANGELOG.​
• I have updated the documentation accordingly

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.
• I have updated the license header for each file (see an example below).

# Copyright (C) 2023 Intel Corporation
#
# SPDX-License-Identifier: MIT

[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: -0.02 ⚠️

Comparison is base (fc1616e) 78.70% compared to head (86d8631) 78.69%.

Additional details and impacted files

@@                Coverage Diff                 @@
##           releases/1.2.0     #967      +/-   ##
==================================================
- Coverage           78.70%   78.69%   -0.02%     
==================================================
  Files                 231      231              
  Lines               26420    26420              
  Branches             5258     5258              
==================================================
- Hits                20795    20790       -5     
- Misses               4400     4402       +2     
- Partials             1225     1228       +3     

Flag	Coverage Δ
macos-11_Python-3.8	?
ubuntu-20.04_Python-3.8	78.69% <ø> (ø)
windows-2019_Python-3.8	?

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see 2 files with indirect coverage changes

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[vinnamkim]

LGTM.