[Docs] Update link in `docs/sql/tutorials/mindsdb-superset-snowflake.mdx`

[martyna-mindsdb]

Instructions

1. Go to the docs/sql/tutorials/mindsdb-superset-snowflake.mdx file.

2. Search for [Slack](https://join.slack.com/t/mindsdbcommunity/shared_invite/zt-o8mrmx3l-5ai~5H66s6wlxFfBMVI6wQ) and replace it with [Slack](https://mindsdb.com/joincommunity)

3. Save your changes and create a PR.

The https://github.com/mindsdb/mindsdb/labels/first-timers-only Label

We are happy to welcome you on board! Please take a look at the rules below for first-time contributors.

1. You can solve only one issue labeled as https://github.com/mindsdb/mindsdb/labels/first-timers-only. After that, please look at other issues labeled as https://github.com/mindsdb/mindsdb/labels/good%20first%20issue, https://github.com/mindsdb/mindsdb/labels/help%20wanted, or https://github.com/mindsdb/mindsdb/labels/integration.

2. Please leave a comment on this issue and wait until you are assigned. Then you can create a PR.

3. After you create your first PR in the MindsDB repository, please sign our CLA to become a MindsDB contributor. You can do that by leaving a comment that contains the following: I have read the CLA Document and I hereby sign the CLA

Thank you for contributing to MindsDB!

[SachinHatikankar100]

Hi @martyna-mindsdb can you please assign this me

[martyna-mindsdb]

@SachinHatikankar100 Please see the issue description - one user can solve only one issue labeled as first-timers-only.

As you have contributed to our repo before, you can have a look at other help-wanted issues.

[SachinHatikankar100]

@martyna-mindsdb noted thanks!

[ananyabhat29]

Hey @martyna-mindsdb Can I take this up?

[martyna-mindsdb]

Hi @ananyabhat29 Sure - you can start working on it.

[Prakriti2003]

Please assign me this issue

[martyna-mindsdb]

@Prakriti2003 You can have a look at unassigned issues labeled as help-wanted.