DOCSP-40541 Update the URLs used to download the agent (#258)

<!-- Add a description of your PR here (optional) -->

- [DOCSP-40541](https://jira.mongodb.org/browse/DOCSP-40541)
-
[STAGING](https://preview-mongodbkanchanamongodb.gatsbyjs.io/ops-manager/DOCSP-40541/core/requirements/#internet-site-access)
- [LATEST BUILD
LOG](https://workerpool-boxgs.mongodbstitch.com/pages/job.html?collName=queue&jobId=6679a466ebce19f314a2b0d3)

### Self-Review Checklist

- [ ]
[Define](https://wiki.corp.mongodb.com/display/DE/Taxonomy+tagging+instructions)
taxonomy
[values](https://wiki.corp.mongodb.com/display/DE/Docs+Taxonomy) at top
of page.
- [ ] Add genre facets (tutorial or reference), as in this [example
PR](10gen/cloud-docs#5042).
- [ ] Add programmingLanguage (if necessary).
- [ ] Add meta keywords (if necessary).
- [ ] Resolve any new warnings or errors in the build.
- [ ] Proofread for spelling and grammatical errors.
- [ ] Check staging for rendering issues.
- [ ] Confirm links are working.

Author: kanchana-mongodb

source/includes/list-table-needed-mongodb-sites-over-internet.rst

@@ -4,7 +4,7 @@
 
    * - Site
      - Purpose
-   * - downloads.mongodb.com
+   * - downloads.mongodb.com, downloads.mongodb.org
      - To download :dl:`MongoDB Enterprise Builds <enterprise>`.
    * - opsmanager.mongodb.com
      - To download the MongoDB :opsmgr:`version manifest </reference/glossary/#std-term-version-manifest>`.