[updatecli] Update latest snapshot to 8.19.6-SNAPSHOT (elastic#15624)

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---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

.buildkite/pipeline.schedule-daily.yml

@@ -34,7 +34,7 @@ steps:
       env:
         SERVERLESS: "false"
         FORCE_CHECK_ALL: "true"
-        STACK_VERSION: 8.19.5-SNAPSHOT
+        STACK_VERSION: 8.19.6-SNAPSHOT
         PUBLISH_COVERAGE_REPORTS: "true"
     depends_on:
       - step: "check"
@@ -48,7 +48,7 @@ steps:
       env:
         SERVERLESS: "false"
         FORCE_CHECK_ALL: "true"
-        STACK_VERSION: 8.19.5-SNAPSHOT
+        STACK_VERSION: 8.19.6-SNAPSHOT
         STACK_LOGSDB_ENABLED: "true"
         PUBLISH_COVERAGE_REPORTS: "false"
     depends_on:

.buildkite/pipeline.schedule-weekly.yml

@@ -21,7 +21,7 @@ steps:
       env:
         SERVERLESS: "false"
         FORCE_CHECK_ALL: "true"
-        STACK_VERSION: 8.19.5-SNAPSHOT
+        STACK_VERSION: 8.19.6-SNAPSHOT
         PUBLISH_COVERAGE_REPORTS: "false"
         ELASTIC_PACKAGE_DISABLE_ELASTIC_AGENT_WOLFI: "true"
     depends_on: