[CI] Update test matrixes

Author: picandocodigo

.ci/test-matrix.yml

@@ -1,6 +1,6 @@
 ---
 STACK_VERSION:
-  - 8.0.0-SNAPSHOT
+  - 8.1-SNAPSHOT
 
 RUBY_TEST_VERSION:
 - 3.1

.github/workflows/main.yml renamed to .github/workflows/8.1.yml

@@ -1,13 +1,13 @@
-name: main
+name: 8.1
 on:
   push:
     branches:
-      - main
+      - 8.1
   pull_request:
     branches:
-      - main
+      - 8.1
 jobs:
-  test-main:
+  test-8.1:
     env:
       TEST_ES_SERVER: http://localhost:9250
       PORT: 9250
@@ -26,7 +26,7 @@ jobs:
         sudo sysctl -w vm.max_map_count=262144
     - uses: elastic/elastic-github-actions/elasticsearch@master
       with:
-        stack-version: 8.0.0-SNAPSHOT
+        stack-version: 8.1-SNAPSHOT
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby }}