Updated ci configuration

Author: delvedor

.ci/test-matrix.yml

@@ -1,6 +1,6 @@
 ---
 STACK_VERSION:
-  - 7.x-SNAPSHOT
+  - 7.12.0-SNAPSHOT
 
 NODE_JS_VERSION:
   - 14

.github/workflows/nodejs.yml

@@ -86,7 +86,7 @@ jobs:
     - name: Runs Elasticsearch
       uses: elastic/elastic-github-actions/elasticsearch@master
       with:
-        stack-version: 7.x-SNAPSHOT
+        stack-version: 7.12.0-SNAPSHOT
 
     - name: Use Node.js ${{ matrix.node-version }}
       uses: actions/setup-node@v1