Update HPO documentation

[eunwoosh]

Summary

This PR updates HPO documentation.
Additionally, I removed unnecessary part in HPO.

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 e2e tests for validation.
• I have added the description of my changes into CHANGELOG in my target branch (e.g., CHANGELOG in develop).​
• I have updated the documentation in my target branch accordingly (e.g., documentation in develop).
• I have linked related issues.

License

• I submit my code changes under the same Apache 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) 2024 Intel Corporation
# SPDX-License-Identifier: Apache-2.0

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 80.07%. Comparing base (b0c8583) to head (8d8830b).
Report is 11 commits behind head on releases/2.0.0.

Files	Patch %	Lines
src/otx/hpo/hpo_runner.py	0.00%	1 Missing ⚠️
src/otx/hpo/resource_manager.py	92.30%	1 Missing ⚠️

Additional details and impacted files

@@                Coverage Diff                 @@
##           releases/2.0.0    #3235      +/-   ##
==================================================
- Coverage           80.09%   80.07%   -0.03%     
==================================================
  Files                 186      186              
  Lines               15386    15397      +11     
==================================================
+ Hits                12324    12329       +5     
- Misses               3062     3068       +6     

Flag	Coverage Δ
py310	80.07% <87.50%> (-0.03%)	⬇️
py311	80.07% <87.50%> (-0.03%)	⬇️

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