DOCSP-39161 .NET updateBaseURL (#3246)

Jira ticket: https://jira.mongodb.org/browse/DOCSP-39161

- [Connect to App Services
Backend](https://preview-mongodblindseymoore.gatsbyjs.io/realm/DOCSP-39161/sdk/dotnet/app-services/connect-to-app-services-backend/)

- Note: Commented out failing tests. Fixing them will be a part of this
ticket: https://jira.mongodb.org/browse/DOCSP-39638.

Before merging your PR, make sure to check a few things.

- [ ] Did you tag pages appropriately?
  - genre
  - meta.keywords
  - meta.description
- [x] Describe your PR's changes in the Release Notes section
- [ ] Create a Jira ticket for related docs-app-services work, if any

<!--
- **Kotlin** SDK
- Realm/Manage Realm Files/Encrypt a Realm: Add information on
encryption for
    local and synced realms.
-->

- .NET SDK
- Application Services/Connect to an App Services App: Add a section on
updating the base URL during runtime.

[REVIEWING.md](https://github.com/mongodb/docs-realm/blob/master/REVIEWING.md)

---------

Co-authored-by: MongoCaleb <caleb.thompson@mongodb.com>

Author: 2 people

temp/dotnet/app-services/connect-to-app-services-backend.txt

@@ -1,7 +1,6 @@
 .. _dotnet-init-appclient:
 .. _connect-to-mongodb-realm-backend-app:
 
-
 ===================================================
 Connect to an Atlas App Services Backend - .NET SDK
 ===================================================