Fix additional arguments help in dotnet test

[sbaid]

Description

dotnet test -h displays this in help.

Usage: dotnet test [arguments] [options] [args]
...
Additional Arguments:
Any extra commandline runsettings arguments that should be passed to vstest. See 'dotnet vstest 
--help' for available options.
                                        Example: -- RunConfiguration.ResultsDirectory="C:\users\user\desktop\Results Directory" MSTest.DeploymentEnabled=false

suggest change first line to

Usage: dotnet test [arguments] [options] [[--] <args>...]]
...
args: 
      Any extra arguments that should be passed to test adapter. Arguments may be specified as name-value pair of the form <n>=<v>, where <n> is the argument name, and <v> is the argument value. Use a space to separate multiple arguments.
    Example:  MSTest.DeploymentEnabled=false

<add  a aka.ms link that details out additional arguments documentation with example>

This help caused the confusion referenced in this https://github.com/dotnet/cli/issues/5659

Steps to reproduce

What steps can reproduce the defect?
Please share the setup, commandline for vstest.console, sample project, target
framework etc.

Expected behavior

Share the expected output

Actual behavior

What is the behavior observed?

Environment

Please share additional details about the test environment.
Operating system, Build version of vstest.console

[sbaid]

/cc @davidfowl

[Faizan2304]

Fixed!!