fix(dependabot): Fix dependabot.yaml commit-message (#333)

For some reason, the dependabot file checker decided to wake up after
rebasing some random branch to main:

https://github.com/canonical/ubuntu-pro-for-windows/runs/17597569230

File `dependabot.yaml` is wrong, as seen in the fact that the PR is
opens are not prefixed as specified.

Anyways, the issue is just a typo. See the
[documentation](https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#commit-message).

.github/dependabot.yml

@@ -2,49 +2,49 @@ version: 2
 updates:
   - package-ecosystem: "gomod"
     directory: "/agentapi"
-    commit_message:
+    commit-message:
       prefix: "deps(agentapi): "
     schedule:
       interval: "daily"
 
   - package-ecosystem: "gomod"
     directory: "/windows-agent"
-    commit_message:
+    commit-message:
       prefix: "deps(windows-agent): "
     schedule:
       interval: "daily"
 
   - package-ecosystem: "gomod"
     directory: "/common"
-    commit_message:
+    commit-message:
       prefix: "deps(common): "
     schedule:
       interval: "daily"
 
   - package-ecosystem: "gomod"
     directory: "/end-to-end"
-    commit_message:
+    commit-message:
       prefix: "deps(end-to-end): "
     schedule:
       interval: "daily"
 
   - package-ecosystem: "gomod"
     directory: "/tools"
-    commit_message:
+    commit-message:
       prefix: "deps(tools): "
     schedule:
       interval: "daily"
 
   - package-ecosystem: "gomod"
     directory: "/wsl-pro-service"
-    commit_message:
+    commit-message:
       prefix: "deps(wsl-pro-service): "
     schedule:
       interval: "daily"
 
   - package-ecosystem: "gomod"
     directory: "/wslserviceapi"
-    commit_message:
+    commit-message:
       prefix: "deps(wslserviceapi): "
     schedule:
       interval: "daily"
@@ -53,27 +53,27 @@ updates:
     # Workflow files stored in the
     # default location of `.github/workflows`
     directory: "/"
-    commit_message:
+    commit-message:
       prefix: "deps(gh-actions): "
     schedule:
       interval: "daily"
 
   - package-ecosystem: "pub"
     # So we update grpc and protobuf packages
     directory: "/agentapi/dart"
-    commit_message:
+    commit-message:
       prefix: "deps(agentapi): "
     schedule:
       interval: "daily"
   - package-ecosystem: "pub"
     directory: "/gui/packages/p4w_ms_store"
-    commit_message:
+    commit-message:
       prefix: "deps(gui-p4w_ms_store): "
     schedule:
       interval: "daily"
   - package-ecosystem: "pub"
     directory: "/gui/packages/ubuntupro"
-    commit_message:
+    commit-message:
       prefix: "deps(gui-ubuntupro): "
     schedule:
       interval: "daily"