Remove Flow references

Amends avajs#2098 and entirely removes Flow references, as support is currently non-existing and retained information is misleading.

Author: langri-sha

docs/recipes/flow.md

@@ -22,7 +22,7 @@ Translations: [Español](https://github.com/avajs/ava-docs/blob/master/es_ES/rea
 - Runs tests concurrently
 - Enforces writing atomic tests
 - No implicit globals
-- Includes TypeScript & Flow type definitions
+- Includes TypeScript
 - [Magic assert](#magic-assert)
 - [Isolated environment for each test file](./docs/01-writing-tests.md#process-isolation)
 - [Write your tests using the latest JavaScript syntax](#latest-javascript-support)
@@ -160,7 +160,6 @@ We have a growing list of [common pitfalls](docs/08-common-pitfalls.md) you may
 - [When to use `t.plan()`](docs/recipes/when-to-use-plan.md)
 - [Browser testing](docs/recipes/browser-testing.md)
 - [TypeScript](docs/recipes/typescript.md)
-- [Flow](docs/recipes/flow.md)
 - [Configuring Babel][Babel recipe]
 - [Using ES modules](docs/recipes/es-modules.md)
 - [Passing arguments to your test files](docs/recipes/passing-arguments-to-your-test-files.md)