Increase minimum friendsofsymfony/http-cache to ^2.6

Author: alexander-schranz

composer.json

@@ -22,7 +22,7 @@
     ],
     "require": {
         "php": "^7.2",
-        "friendsofsymfony/http-cache": "^2.5.2",
+        "friendsofsymfony/http-cache": "^2.6",
         "symfony/framework-bundle": "^3.4.4 || ^4.1.12 || ^5.0",
         "symfony/http-foundation": "^3.4.4 || ^4.1.12 || ^5.0",
         "symfony/http-kernel": "^3.4.4 || ^4.1.12 || ^5.0"