[KYUUBI #2905][DOCS] Update the number of new committers in MATURITY.md

### _Why are the changes needed?_

update new committers number: 2 -> 6

### _How was this patch tested?_
- [ ] Add some test cases that check the changes thoroughly including negative and positive cases if possible

- [ ] Add screenshots for manual tests if appropriate

- [ ] [Run test](https://kyuubi.apache.org/docs/latest/develop_tools/testing.html#running-tests) locally before make a pull request

Closes #2913 from ulysses-you/committer.

Closes #2905

e088a5e [ulysses-you] 6

Authored-by: ulysses-you <ulyssesyou18@gmail.com>
Signed-off-by: ulysses-you <ulyssesyou@apache.org>

Author: ulysses-you

MATURITY.md

@@ -76,7 +76,7 @@ Mentors and community members are encouraged to contribute to this page and comm
 | CO10 | The project has a well-known homepage that points to all the information required to operate according to this maturity model.                                         | :white_check_mark: The website describes of the project with download, user manual, technical details, how to contribute and team introduce.                                                                                          |
 | CO20 | The community welcomes contributions from anyone who acts in good faith and in a respectful manner, and who adds value to the project.                                 | :white_large_square: Committers are really welcome contributions and the community is actively seeking for new committers. The community has elected 0 new PPMC members and 2 new committers during incubation, based on meritocracy. |
 | CO30 | Contributions include source code, documentation, constructive bug reports, constructive discussions, marketing and generally anything that adds value to the project. | :white_check_mark: The community welcomes all contributions. The contribution guide refers to non source code contribution. The community is very clear about contributions being more than code.                                     |
-| CO40 | The community strives to be meritocratic and gives more rights and responsibilities to contributors who, over time, add value to the project.                          | :white_large_square:. The community has elected 0 new PPMC members and 2 new committers during incubation, based on meritocracy.                                                                                                      |
+| CO40 | The community strives to be meritocratic and gives more rights and responsibilities to contributors who, over time, add value to the project.                          | :white_large_square:. The community has elected 0 new PPMC members and 6 new committers during incubation, based on meritocracy.                                                                                                      |
 | CO50 | The project documents how contributors can earn more rights such as commit access or decision power, and applies these principles consistently.                        | :x: ~The process to become a committer or PPMC member is documented on the website~. see, https://community.apache.org/newcommitter.html                                                                                              |
 | CO60 | The community operates based on consensus of its members (see CS10) who have decision power. Dictators, benevolent or not, are not welcome in Apache projects.         | :white_large_square: The project works to build consensus. All PPMC votes have been unanimous so far.                                                                                                                                 |
 | CO70 | The project strives to answer user questions in a timely manner.                                                                                                       | :white_large_square: The project typically provides detailed answers to user questions within a few days via dev mailing list, GitHub issues and Github Discussions.                                                                  |