Removes prefix from dependabot's commit message (#3548)

### Description
Removes prefix from dependabot's commit message since it is removed when
generating releases notes ultimately.


### Check List
~- [ ] New functionality includes testing~
~- [ ] New functionality has been documented~
- [x] Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and
signing off your commits, please check
[here](https://github.com/opensearch-project/OpenSearch/blob/main/CONTRIBUTING.md#developer-certificate-of-origin).

Signed-off-by: Darshit Chanpura <[email protected]>

.github/dependabot.yml

@@ -4,8 +4,6 @@ updates:
     directory: "/"
     schedule:
       interval: "weekly"
-    commit-message:
-      prefix: "dependabot:"
     ignore:
       # For all packages, ignore all major versions to minimize breaking issues
       - dependency-name: "*"
@@ -14,5 +12,3 @@ updates:
     directory: "/"
     schedule:
       interval: "weekly"
-    commit-message:
-      prefix: "dependabot:"