update dependencies; types correction

Author: mmasiukevich

.travis.yml

@@ -1,7 +1,6 @@
 language: php
 
 php:
-  - 7.3
   - 7.4
 
 services:

README.md

@@ -1,7 +1,7 @@
 ## What is it?
-[![Build Status](https://travis-ci.org/php-service-bus/mutex.svg?branch=v4.0)](https://travis-ci.org/php-service-bus/mutex)
-[![Code Coverage](https://scrutinizer-ci.com/g/php-service-bus/mutex/badges/coverage.png?b=v4.0)](https://scrutinizer-ci.com/g/php-service-bus/mutex/?branch=v4.0)
-[![Scrutinizer Code Quality](https://scrutinizer-ci.com/g/php-service-bus/mutex/badges/quality-score.png?b=v4.0)](https://scrutinizer-ci.com/g/php-service-bus/mutex/?branch=v4.0)
+[![Build Status](https://travis-ci.org/php-service-bus/mutex.svg?branch=v4.1)](https://travis-ci.org/php-service-bus/mutex)
+[![Code Coverage](https://scrutinizer-ci.com/g/php-service-bus/mutex/badges/coverage.png?b=v4.1)](https://scrutinizer-ci.com/g/php-service-bus/mutex/?branch=v4.1)
+[![Scrutinizer Code Quality](https://scrutinizer-ci.com/g/php-service-bus/mutex/badges/quality-score.png?b=v4.1)](https://scrutinizer-ci.com/g/php-service-bus/mutex/?branch=v4.1)
 
 This component is part of the [PHP Service Bus](https://github.com/php-service-bus/service-bus): mutexes implementation.
 > The code is partly based on the [amp/sync](https://github.com/amphp/sync) project.

composer.json

@@ -27,16 +27,16 @@
     }
   },
   "require": {
-    "php": ">=7.3",
+    "php": ">=7.4",
     "amphp/amp": "v2.4.*",
     "amphp/file": "v1.0.*",
     "amphp/redis": "v1.0.*"
   },
   "require-dev": {
     "php-service-bus/code-style-config": "v1.2.*",
-    "phpunit/phpunit": "v8.4.*",
-    "vimeo/psalm": "v3.7.*",
-    "phpstan/phpstan": "v0.11.*"
+    "phpunit/phpunit": "v9.1.*",
+    "vimeo/psalm": "v3.11.*",
+    "phpstan/phpstan": "v0.12.*"
   },
   "prefer-stable": true,
   "minimum-stability": "dev",