ci: set prefix commit message dependabot (#748)

Author: NguyenHoangSon96

.github/dependabot.yml

@@ -4,4 +4,6 @@ updates:
     directory: "/"
     schedule:
       interval: "monthly"
+    commit-message:
+        prefix: "chore(deps): "
     open-pull-requests-limit: 10

CHANGELOG.md

@@ -5,6 +5,7 @@
 1. [#724](https://github.com/influxdata/influxdb-client-csharp/pull/724): Set snapshot version properly in ci-deploy-snapshot.sh
 1. [#728](https://github.com/influxdata/influxdb-client-csharp/pull/728): Set up auto merge dependabot workflow.
 1. [#738](https://github.com/influxdata/influxdb-client-csharp/pull/738): The token in the Management API is no longer plain text.
+1. [#748](https://github.com/influxdata/influxdb-client-csharp/pull/748): Set prefix commit message for dependabot.  
 
 ## 5.0.0 [2026-01-13]