Adjust README

Author: martin-helmich

README.md

@@ -32,10 +32,10 @@ issue, or (better yet) a pull request.
 
 There are several release branches of this library, each of these being compatible with different releases of PHPUnit and PHP. The following table should give an easy overview:
 
-| "Mongomock" version | PHPUnit 4 | PHPUnit 5 | PHPUnit 6 | PHPUnit 7 | PHPUnit 8 |
-| ------------------------ | --------- | --------- | --------- | --------- | --------- |
-| v1 (branch `v1`), **unsupported** | :no_entry_sign: | :white_check_mark: | :no_entry_sign: | :no_entry_sign: | :no_entry_sign: |
-| v2 (branch `master`) | :no_entry_sign: | :no_entry_sign: | :white_check_mark: | :white_check_mark: | :white_check_mark: |
+| "Mongomock" version | PHPUnit 4 | PHPUnit 5 | PHPUnit 6 | PHPUnit 7 | PHPUnit 8 | PHPUnit 9 |
+| ------------------- | --------- | --------- | --------- | --------- | --------- | --------- |
+| v1 (branch `v1`), **unsupported** | :no_entry_sign: | :white_check_mark: | :no_entry_sign: | :no_entry_sign: | :no_entry_sign: | :no_entry_sign: |
+| v2 (branch `master`) | :no_entry_sign: | :no_entry_sign: | :white_check_mark: | :white_check_mark: | :white_check_mark: | :white_check_mark: |
 
 When you are using `composer require` and have already declared a dependency to `phpunit/phpunit` in your `composer.json` file, Composer should pick latest compatible version automatically.