fix: update to latest cli install commands (#43407)

Author: ajpinedam

docs/core/tools/custom-templates.md

@@ -243,7 +243,7 @@ dotnet new install <NUGET_PACKAGE_ID>
 Provide a custom NuGet source (for example, `https://api.my-custom-nuget.com/v3/index.json`).
 
 ```dotnetcli
-dotnet new --install <NUGET_PACKAGE_ID> --nuget-source <SOURCE>
+dotnet new install <NUGET_PACKAGE_ID> --nuget-source <SOURCE>
 ```
 
 ### To install a template package from a local nupkg file

docs/core/tools/dotnet-new-install.md

@@ -94,7 +94,7 @@ Starting with .NET SDK 6.0.100, installed template packages are available in lat
 - Install version 2.0 of the SPA templates for ASP.NET Core from a custom NuGet source using interactive mode:
 
   ```dotnetcli
-  dotnet new --install Microsoft.DotNet.Web.Spa.ProjectTemplates::2.0.0 --add-source "https://api.my-custom-nuget.com/v3/index.json" --interactive
+  dotnet new install Microsoft.DotNet.Web.Spa.ProjectTemplates::2.0.0 --add-source "https://api.my-custom-nuget.com/v3/index.json" --interactive
   ```
 
 ## See also