Nginx-ingress removal from silta-cluster subcharts

[Jancis]

We're referencing a fairly old nginx-ingress subchart (0.17.1). The referenced chart has become unavailable and yields test build errors. This change removes it from default installation set, suggests manual installation of the official chart.

Note: This applies to silta-cluster installations using Nginx Inc. ingress, only installations with nginx-ingress.enabled: true are affected. Installations with ingress-nginx.enabled: true are not affected by this removal. This change will also remove the related naming confusion :)

[Copilot]

Pull Request Overview

This PR removes the nginx-ingress subchart dependency from silta-cluster to resolve build errors caused by the unavailable chart version (0.17.1), while providing migration guidance for existing users.

• Removed nginx-ingress subchart from Chart.yaml dependencies and values.yaml configuration
• Added comprehensive upgrade documentation with manual installation instructions
• Updated README.md to remove nginx-ingress repository references and add upgrade path

Reviewed Changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 2 comments.

File	Description
silta-cluster/values.yaml	Removes nginx-ingress configuration section (48 lines)
silta-cluster/docs/Upgrading-to-1.10.0.md	Adds new upgrade guide with manual installation steps for nginx-ingress
silta-cluster/README.md	Removes nginx-ingress repo setup and adds reference to upgrade documentation
silta-cluster/Chart.yaml	Bumps version to 1.10.0 and removes nginx-ingress dependency

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[Copilot]

There's an extra space in the markdown link syntax. It should be using [Nginx Inc. ingress] instead of using[ Nginx Inc. ingress].

Suggested change

	This applies to silta-cluster installations using[ Nginx Inc. ingress](https://github.com/nginxinc/kubernetes-ingress/), only installations with `nginx-ingress.enabled: true` are affected. Installations with `ingress-nginx.enabled: true` are not affected by this removal, you don't have to do anything.
	This applies to silta-cluster installations using [Nginx Inc. ingress](https://github.com/nginxinc/kubernetes-ingress/), only installations with `nginx-ingress.enabled: true` are affected. Installations with `ingress-nginx.enabled: true` are not affected by this removal, you don't have to do anything.

[Copilot]

Two issues in this line: 'kubernete-ingress' should be 'kubernetes-ingress', and there's a duplicate word 'using using' which should be just 'using'.

Suggested change

	Nginx Inc. [kubernete-ingress](https://github.com/nginxinc/kubernetes-ingress/) load balancer is removed from silta-cluster subchart list, but it is still compatible with ingresses and resources. If you want to keep using using it, you have to install the nginx-ingress manually.
	Nginx Inc. [kubernetes-ingress](https://github.com/nginxinc/kubernetes-ingress/) load balancer is removed from silta-cluster subchart list, but it is still compatible with ingresses and resources. If you want to keep using it, you have to install the nginx-ingress manually.