docs: Use 'dotnet new install' instead of deprecated --install switch (#987)

This is to avoid dotnet warning:

Warning: use of 'dotnet new --install' is deprecated. Use 'dotnet new
install' instead.

Author: mloskot

docs/docs/operator/getting-started.mdx

@@ -24,7 +24,7 @@ For local development, we recommend using `kind` or Docker Desktop as it provide
 KubeOps provides templates to help you get started quickly. Install them using the .NET CLI:
 
 ```bash
-dotnet new --install KubeOps.Templates::*
+dotnet new install KubeOps.Templates
 ```
 
 KubeOps offers several template types:

src/KubeOps.Templates/README.md

@@ -15,7 +15,7 @@ To install the template package, use the `dotnet` cli
 (or you may use the exact version as provided in the link above):
 
 ```bash
-dotnet new --install KubeOps.Templates::*
+dotnet new install KubeOps.Templates
 ```
 
 As soon as the templates are installed, you may use them with the short names below: