Project governance: tweak voting majority threshold

### Describe the bug

Currently, the voting requires 2/3 majority which is described in [Voting](https://github.com/fluent/fluentd/blob/master/GOVERNANCE.md#voting)

More contributors involved, it tends to be hard to satisfy with 2/3 majority if there are many inactive maintainers in the future.

Also mentioned https://github.com/fluent/fluentd/issues/4150#issuecomment-1507874478

### To Reproduce

N/A

### Expected behavior

Introduce the new threshold in a practical manner.

Instead of 2/3 majority, changes the threshold like this:

**UPDATED**: based on https://github.com/fluent/fluentd/issues/4151#issuecomment-1526998656

* No objection ballot
* At least effective **3-person** affirmative vote
* At least effective **2-organization** affirmative vote
* Effective organization affirmative vote means:
* One member of the organization made an affirmative vote (even though other colleagues didn't vote, it was treated as an effective affirmative organization vote)
* An affirmative vote of a member not belonging to an organization is considered as one organization's affirmative vote
* At least **2-week** for voting

Some ballot scenario:

* effective 3-person (all individual) affirmative vote 🙋🙋‍♂️🙋‍♀️=> approved
* effective 3-person (1 individual🙋, 2 person who belong to the same organization🙋‍♂️🙋‍♂️) affirmative vote => approved
* effective 3-person (1 organization🙋, 2 individuals🙋‍♂️🙋‍♀️) => approved

* effective 3-person but, who belong to the same organization 🙋🙋🙋 => declined
* effective 3-person but 1 objection 🙋🙋🙅‍♂️ => declined

The important point is not to be dominated by certain organizations and to make the project's decisions by maintainers appropriately.

### Your Environment

```markdown
N/A
```

### Your Configuration

```apache
N/A
```

### Your Error Log

```shell
N/A
```

### Additional context

* If these change was introduced, [the previous organization's vote](https://github.com/fluent/fluentd/pull/4069) was easy to make things forward.
* Before call for voting #4150, this issue should be processed. (it makes easy to process #4150 afterwards)

* well-known similar voting threshold is mentioned https://github.com/fluent/fluentd/issues/4150#issuecomment-1507874478

ref: `code modifications` and `veto` of `Apache Voting Process`
* https://www.apache.org/foundation/voting#apache-voting-process
> the proposal requires three positive votes and no negative votes in order to pass

For the record, the previous proposal:

* ~~No objection ballot~~
* ~~At least effective 3-organization affirmative vote~~

~~Both of the above conditions are met, the voting agenda will be approved.~~