Edit DorisConfigOptions withDescription

[Zhumengze]

Proposed changes

Issue Number: close #xxx

Problem Summary:

The DorisConfigOptions class has an incorrect description of the "doris.exec.mem.limit" parameter,
Change to correct description

Checklist(Required)

1. Does it affect the original behavior: (Yes/No/I Don't know)
   No
2. Has unit tests been added: (Yes/No/No Need)
   No
3. Has document been added or modified: (Yes/No/No Need)
   No
4. Does it need to update dependencies: (Yes/No)
   No
5. Are there any changes that cannot be rolled back: (Yes/No)
   No

Further comments

If this is a relatively large or complex change, kick off the discussion at [email protected] by explaining why you chose the solution you did and what alternatives you considered, etc...