Pin psr7-integration-tests to v1.1 in 1.6.x

For version 1.6.x, pin psr7-integration-tests to v1.1.

Author: akrabat

composer.json

@@ -39,7 +39,7 @@
     "ext-json": "*",
     "adriansuter/php-autoload-override": "^1.3",
     "http-interop/http-factory-tests": "^0.9.0",
-    "php-http/psr7-integration-tests": "dev-master",
+    "php-http/psr7-integration-tests": "1.1",
     "phpspec/prophecy": "^1.15",
     "phpspec/prophecy-phpunit": "^2.0",
     "phpstan/phpstan": "^1.8",