build: use v2 psr http message (#440)

Author: Greg Bowler

composer.json

@@ -10,7 +10,7 @@
 		"ext-mbstring": "*",
 		"phpgt/cssxpath": "^1.1",
 		"phpgt/propfunc": "^1.0",
-		"psr/http-message": "^1.0"
+		"psr/http-message": "^2.0"
 	},
 
 	"require-dev": {