Update possibly needed for .NET 7 in instructions for installation of Bolero template on Bolero website.

[BentTranberg]

When running the instructions, the following appears.

C:\devbox\BugHunt24>dotnet new -i Bolero.Templates
Warning: use of 'dotnet new --install' is deprecated. Use 'dotnet new install' instead.
For more information, run:
   dotnet new install -h

The following template packages will be installed:
   Bolero.Templates

Bolero.Templates (version 0.17.12) is already installed, it will be replaced with latest version.
Bolero.Templates::0.17.12 was successfully uninstalled.
Success: Bolero.Templates::0.20.4 installed the following templates:
Template Name              Short Name  Language  Tags
-------------------------  ----------  --------  -----------------
Bolero Hosted Application  bolero-app  F#        Web/Blazor/Bolero


C:\devbox\BugHunt24>

I don't know whether it's best to just leave the instructions as is in order to cover all .NET versions with the least amount of instructions, or to add information in order to avoid the warning seen here.

[Tarmil]

I think I'll leave the instructions for now, and probably update them for .NET 8 (which is the next LTS release).