run CI on ruby 3.3

Author: nov

.github/workflows/spec.yml

@@ -3,7 +3,7 @@ name: Spec
 on:
   push:
     branches:
-      - master
+      - main
   pull_request:
 
 permissions:
@@ -14,7 +14,7 @@ jobs:
     strategy:
       matrix:
         os: ['ubuntu-20.04', 'ubuntu-22.04']
-        ruby-version: ['3.1', '3.2']
+        ruby-version: ['3.1', '3.2', '3.3']
         include:
         - os: 'ubuntu-20.04'
           ruby-version: '3.0'