[ZEPPELIN-6354] Remove repo.hortonworks.com

### What is this PR for?
This PR removes the Hortonworks repository from the `vendor-repo` Maven profile in the root pom.xml. The Hortonworks repository's SSL certificate has recently expired, and since Hortonworks was acquired by Cloudera, maintaining a separate repository entry is no longer necessary.

### What type of PR is it?
Bug Fix

### Todos
* [x] - Remove Hortonworks repository from vendor-repo profile
* [x] - Verify that vendor-repo profile is not used in CI/CD pipelines
* [x] - Confirm no dependencies explicitly require Hortonworks repository

### What is the Jira issue?
* [ZEPPELIN-6354](https://issues.apache.org/jira/browse/ZEPPELIN-6354)

### How should this be tested?
* Verify that the build completes successfully without the Hortonworks repository:
  ```bash
  ./mvnw clean install -DskipTests
  ```
* Confirm that the vendor-repo profile (if manually activated) still works with Cloudera repository:
  ```bash
  ./mvnw clean install -DskipTests -Pvendor-repo
  ```
* Check that no dependencies are downloaded from the Hortonworks repository during build

### Screenshots (if appropriate)
N/A

### Questions:
* Does the license files need to update? No
* Is there breaking changes for older versions? No
* Does this needs documentation? No

### Additional Notes:
- The `vendor-repo` profile is not currently used in any GitHub Actions workflows
- Cloudera repository is retained in the profile for potential vendor-specific artifacts
- Future consideration: The entire `vendor-repo` profile could be removed if not needed, as CI/CD pipelines don't use it



Closes apache#5103 from kmularise/ZEPPELIN-6354.

Signed-off-by: Philipp Dallig <[email protected]>

Author: kmularise

pom.xml

@@ -798,10 +798,6 @@
           <id>cloudera</id>
           <url>https://repository.cloudera.com/artifactory/cloudera-repos/</url>
         </repository>
-        <repository>
-          <id>hortonworks</id>
-          <url>https://repo.hortonworks.com/content/groups/public/</url>
-        </repository>
       </repositories>
     </profile>