Prepare for v1.27

Author: nicolas-grekas

composer.json

@@ -29,7 +29,7 @@
     "minimum-stability": "dev",
     "extra": {
         "branch-alias": {
-            "dev-main": "1.26-dev"
+            "dev-main": "1.27-dev"
         },
         "thanks": {
             "name": "symfony/polyfill",