Change the introduction part of clean documentation

[qidanrui]

Description

Change the introduction part of clean documentation for release

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have already squashed the commits and make the commit message conform to the project standard.
• [x] I have already marked the commit with "BREAKING CHANGE" or "Fixes #" if needed.
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules

[codecov[bot]]

Codecov Report

Merging #720 (c7b41ff) into develop (7e2a5a0) will increase coverage by 57.32%. The diff coverage is n/a.

:exclamation: Current head c7b41ff differs from pull request most recent head 862b447. Consider uploading reports for the commit 862b447 to get more accurate results

@@             Coverage Diff              @@
##           develop     #720       +/-   ##
============================================
+ Coverage         0   57.32%   +57.32%     
============================================
  Files            0      288      +288     
  Lines            0    18145    +18145     
============================================
+ Hits             0    10401    +10401     
- Misses           0     7744     +7744     

Impacted Files	Coverage Δ
dataprep/clean/clean_fi_alv.py	25.00% <0.00%> (ø)
dataprep/clean/clean_pe_ruc.py	22.44% <0.00%> (ø)
dataprep/clean/clean_country.py	93.75% <0.00%> (ø)
dataprep/datasets/_base.py	92.85% <0.00%> (ø)
dataprep/clean/clean_gr_amka.py	22.91% <0.00%> (ø)
dataprep/clean/address_utils.py	100.00% <0.00%> (ø)
dataprep/eda/eda_frame.py	86.54% <0.00%> (ø)
dataprep/clean/clean_lat_long.py	86.22% <0.00%> (ø)
dataprep/clean/clean_at_uid.py	25.58% <0.00%> (ø)
dataprep/clean/utils.py	40.00% <0.00%> (ø)
... and 278 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 7e2a5a0...862b447. Read the comment docs.