bump dependencies

Bump phpstan/phpstan from 0.11.19 to 0.11.20

Bumps [phpstan/phpstan](https://github.com/phpstan/phpstan) from 0.11.19 to 0.11.20.
- [Release notes](https://github.com/phpstan/phpstan/releases)
- [Commits](https://github.com/phpstan/phpstan/compare/0.11.19...0.11.20)

Signed-off-by: dependabot[bot] <[email protected]>

2.0.0

upgraded minimum php to 7.4.

for 7.2/7.3, use versions <2

1.3.0

Add conversion option

1.2.1

new key

1.2.0

updated composer files

1.1.0

phpcs fix

1.0.2

added 7.2 build to travis

First stable

1.0.1

renamed namespaces