[CI] Update Stack version on GitHub Actions

Author: picandocodigo

Diff for: .github/workflows/2.4.yml

@@ -24,7 +24,7 @@ jobs:
         sudo sysctl -w vm.max_map_count=262144
     - uses: elastic/elastic-github-actions/elasticsearch@master
       with:
-        stack-version: 7.9.0
+        stack-version: 7.x-SNAPSHOT
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: 2.4

Diff for: .github/workflows/2.5.yml

@@ -24,7 +24,7 @@ jobs:
         sudo sysctl -w vm.max_map_count=262144
     - uses: elastic/elastic-github-actions/elasticsearch@master
       with:
-        stack-version: 7.9.0
+        stack-version: 7.x-SNAPSHOT
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: 2.5

Diff for: .github/workflows/2.6.yml

@@ -24,7 +24,7 @@ jobs:
         sudo sysctl -w vm.max_map_count=262144
     - uses: elastic/elastic-github-actions/elasticsearch@master
       with:
-        stack-version: 7.9.0
+        stack-version: 7.x-SNAPSHOT
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: 2.6

Diff for: .github/workflows/2.7.yml

@@ -24,7 +24,7 @@ jobs:
         sudo sysctl -w vm.max_map_count=262144
     - uses: elastic/elastic-github-actions/elasticsearch@master
       with:
-        stack-version: 7.9.0
+        stack-version: 7.x-SNAPSHOT
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: 2.7

Diff for: .github/workflows/jruby.yml

@@ -24,7 +24,7 @@ jobs:
         sudo sysctl -w vm.max_map_count=262144
     - uses: elastic/elastic-github-actions/elasticsearch@master
       with:
-        stack-version: 7.9.0
+        stack-version: 7.x-SNAPSHOT
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: jruby-9.2