AP-1639 Update major version

Author: rajatsib

README.md

@@ -22,7 +22,7 @@ PHP 5.6 and later
 To install the bindings via [Composer](http://getcomposer.org/):
 
 ```
-composer require sendinblue/api-v3-sdk "7.x.x"
+composer require sendinblue/api-v3-sdk "8.x.x"
 ```
 
 Further do:

composer.json

@@ -37,7 +37,7 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "7.x.x-dev"
+            "dev-master": "8.x.x-dev"
         }
     }
 }