[CI] Updates STACK_VERSION, gh actions

Author: picandocodigo

.buildkite/pipeline.yml

@@ -4,7 +4,7 @@ steps:
       provider: "gcp"
     env:
       RUBY_VERSION: "{{ matrix.ruby }}"
-      STACK_VERSION: 8.16.0-SNAPSHOT
+      STACK_VERSION: 8.18.0-SNAPSHOT
     matrix:
       setup:
         ruby:

.github/workflows/testing.yml

@@ -1,3 +1,4 @@
+---
 name: main
 on: [push, pull_request]
 
@@ -27,7 +28,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [ jruby-9.3, jruby-9.4 ]
+        ruby: ['jruby-9.3', 'jruby-9.4']
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4