Update documentation pages that previously mentioned Copilot to reflect Pulumi Neo

[asafashirov]

Following the recent revert of the Pulumi Neo banner that was temporarily added to documentation pages, we need to update the actual content of affected pages to correctly reference Pulumi Neo (instead of Copilot) directly in the text.

The Neo banner was appropriate for blog posts (point-in-time content) but not for docs, where content should reflect the current state of the product. The previous revert PR (#16407) removed the banner from 17 documentation pages. This issue tracks updating those pages to reflect Neo accurately.

Affected pages:

content/docs/administration/access-identity/rbac/scopes/org-settings.md
content/docs/ai/get-started/_index.md
content/docs/deployments/get-started/_index.md
content/docs/deployments/get-started/onboarding-guide/choose-subscription.md
content/docs/deployments/get-started/what-is-it.md
content/docs/iac/cli/commands/pulumi_destroy.md
content/docs/iac/cli/commands/pulumi_preview.md
content/docs/iac/cli/commands/pulumi_refresh.md
content/docs/iac/cli/commands/pulumi_up.md
content/docs/iac/cli/environment-variables.md
content/docs/iac/comparisons/cloud-template-transpilers/aws-cdk/_index.md
content/docs/insights/discovery/_index.md
content/docs/insights/discovery/get-started/_index.md
content/docs/insights/discovery/get-started/using-resource-explorer.md
content/docs/insights/discovery/visual-import.md
content/docs/reference/cloud-rest-api/_index.md
content/docs/reference/cloud-rest-api/copilot/_index.md