Remove implied default NuGet configuration

[withinfocus]

Type of change

- [ ] Bug fix
- [ ] New feature development
- [ ] Tech debt (refactoring, code cleanup, dependency upgrades, etc)
- [X] Build/deploy pipeline (DevOps)
- [ ] Other

Objective

Removes the default NuGet package source config per renovatebot/renovate#20888 (comment) as we're having issues with Renovate not applying package lock updates with its changes, perhaps because of https://github.com/renovatebot/renovate/blob/2fd071cadf24e4c21a5255f25bc8b521f838d3ff/lib/manager/nuget/artifacts.ts#L73 and how it wants to use an alternative setup.

Code changes

• NuGet.config: Removal with note as to why.

Before you submit

• Please check for formatting errors (dotnet format --verify-no-changes) (required)
• If making database changes - make sure you also update Entity Framework queries and/or migrations
• Please add unit tests where it makes sense to do so (encouraged but not required)
• If this change requires a documentation update - notify the documentation team
• If this change has particular deployment requirements - notify the DevOps team

[bitwarden-bot]

Checkmarx One – Scan Summary & Details – f9f7399a-9e30-40bf-860b-f66bbf822538

New Issues

Severity	Issue	Source File / Package	Checkmarx Insight
	Missing User Instruction	/Dockerfile: 1	A user should be specified in the dockerfile, otherwise the image will run as root
	Apt Get Install Pin Version Not Defined	/Dockerfile: 5	When installing a package, its pin version should be defined
	Apt Get Install Pin Version Not Defined	/Dockerfile: 5	When installing a package, its pin version should be defined

Fixed Issues

Severity	Issue	Source File / Package	Checkmarx Insight
	Missing User Instruction	/Dockerfile: 1	A user should be specified in the dockerfile, otherwise the image will run as root
	Apt Get Install Pin Version Not Defined	/Dockerfile: 5	When installing a package, its pin version should be defined
	Apt Get Install Pin Version Not Defined	/Dockerfile: 5	When installing a package, its pin version should be defined
	Image Version Using 'latest'	/Dockerfile: 1	When building images, always tag them with useful tags which codify version information, intended destination (prod or test, for instance), stabili...