Bump PHP minimum version to 7.3

Author: tomzx

composer.json

@@ -20,7 +20,7 @@
 		"issues": "https://github.com/tomzx/php-semver-checker/issues"
 	},
 	"require": {
-		"php": ">=7.2.29",
+		"php": ">=7.3",
 
 		"hassankhan/config": "^2.0",
 		"nikic/php-parser": "^4.0",
@@ -30,7 +30,7 @@
 	},
 	"require-dev": {
 		"mockery/mockery": "^1.0",
-		"phpunit/phpunit": "^7.0|^8.0|^9.0"
+		"phpunit/phpunit": "^8.0|^9.0"
 	},
 	"bin": [
 		"bin/php-semver-checker"
@@ -47,7 +47,7 @@
 	},
 	"config": {
 		"platform": {
-			"php": "7.2.29"
+			"php": "7.3"
 		}
 	},
 	"extra": {