Fix integration tests

[zhouzhuojie]

Description

Fix #442
The reason is that https://stackoverflow.com/a/66910240, removing MYSQL_USER set in the docker-compose file fixes the problem, note that root is automatically created.

Motivation and Context

How Has This Been Tested?

Types of changes

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

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov-commenter]

Codecov Report

Merging #443 (8f325a3) into master (cb72a9e) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #443   +/-   ##
=======================================
  Coverage   81.75%   81.75%           
=======================================
  Files          27       27           
  Lines        1611     1611           
=======================================
  Hits         1317     1317           
  Misses        214      214           
  Partials       80       80           

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[zhouzhuojie]

@jperichon @sesquipedalian-dev can you take a look and give a stamp?

BTW, a few PRs (#441 #439) are blocked by this, I'm also interested in getting the PR merge permission for flagr related repos, let me know if that works for you.

[sesquipedalian-dev]

Looks good, thanks for the fix