Update version requirement

Author: allflame

composer.json

@@ -12,7 +12,7 @@
     "symfony/console": "~2 || ~3",
     "symfony/http-kernel": "~2 || ~3",
     "symfony/dependency-injection": "~2 || ~3",
-    "code-tool/jaeger-client-php": "~2.5"
+    "code-tool/jaeger-client-php": "~2.6"
   },
   "require-dev": {
     "php-ds/php-ds": "@stable",