Docs: 'Running the Tests' section is out of date

Description of Issue/Question

It looks like this docs section about setting up and running the Salt test suite is out-of-date: https://github.com/saltstack/salt/blob/develop/doc/topics/tutorials/writing_tests.rst

Quote from @gtmanfred from https://github.com/saltstack/salt/pull/51082/files#r246492565:

The docs should really have instructions about using test-kitchen to run the test suite.

There are some examples here https://kitchen.saltstack.com/docs/file/docs/gettingstarted.md

but nothing specific to the salt test suite, which uses just bundle exec kitchen verify and can be configured with the runtests verifier to only run specific tests.

https://kitchen.saltstack.com/docs/file/docs/runtests.md#tests

[s0undt3ch]

Yes, we can.

[Ch3LL]

as an update here. Since our tests have continued to change over the last 6 months we are going to wait until the migration to pytest is complete so we can ensure when we update the test documentation it is all accurate. I will be working with the test working group when that migration is complete to ensure we update all of the required documentation. Juts wanted to update the issue here.