Add note in CONTRIBUTING.md about not asking to be assigned to issues

[tianyizheng02]

Describe your change:

Following #8866, I've added a paragraph to CONTRIBUTING.md explicitly asking contributors to not ask to be assigned to issues. Although we don't assign issues in this repo, this was never actually stated in the contributing guidelines.

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".

[tianyizheng02]

@cclauss@dhruvmanila Could I get a review?

[cclauss]

Nice!!

[cclauss]

It would be nice if this content had a markdown anchor so that we could point visitors directly to it.

Example: #8063 (comment)

[tianyizheng02]

It would be nice if this content had a markdown anchor so that we could point visitors directly to it.

@cclauss That content is already under the Contribution section: https://github.com/TheAlgorithms/Python/blob/master/CONTRIBUTING.md#contribution. Do you mean we should have an even more specific Markdown anchor to point to that specific paragraph?

[cclauss]

Yes. That specific paragraph. Same for need for type hints. Same for need for tests, etc.