fix: mysql version function result

[tisonkun]

I hereby agree to the terms of the GreptimeDB CLA

What's changed and what's your intention?

This closes #2846.

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.

Refer to a related PR or issue link (optional)

[tisonkun]

TRIVIAL AS IS. I don't think it worth to write a test, unless we have a Docker test fixture to use.

[codecov]

Codecov Report

Merging #2884 (5f61c74) into develop (b3ffe5c) will decrease coverage by 0.53%.
Report is 7 commits behind head on develop.
The diff coverage is 100.00%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2884      +/-   ##
===========================================
- Coverage    84.86%   84.34%   -0.53%     
===========================================
  Files          745      749       +4     
  Lines       117222   117893     +671     
===========================================
- Hits         99482    99433      -49     
- Misses       17740    18460     +720