Drop support for PHP 7.2

Signed-off-by: Henrique Moody <henriquemoody@gmail.com>

.travis.yml

@@ -2,7 +2,6 @@ sudo: false
 language: php
 
 php:
-  - 7.2
   - 7.3
   - 7.4
   - nightly

composer.json

@@ -15,7 +15,7 @@
         "sort-packages": true
     },
     "require": {
-        "php": ">=7.2",
+        "php": ">=7.3",
         "respect/stringifier": "^0.2.0",
         "symfony/polyfill-mbstring": "^1.2"
     },
@@ -26,7 +26,7 @@
         "phpstan/phpstan": "^0.12",
         "phpstan/phpstan-deprecation-rules": "^0.12",
         "phpstan/phpstan-phpunit": "^0.12",
-        "phpunit/phpunit": "^7.5",
+        "phpunit/phpunit": "^9.3",
         "respect/coding-standard": "^2.1",
         "squizlabs/php_codesniffer": "^3.5",
         "symfony/validator": "^3.0||^4.0",

docs/installation.md

@@ -7,4 +7,4 @@ you can install it using [Composer](http://getcomposer.org).
 composer require respect/validation
 ```
 
-Works on PHP 7.2 or above.
+Works on PHP 7.3 or above.