Options schema should allow spacing after @pre for requires

[BernieWhite]

Description of the issue

The PSRule options schema currently doesn't allow the following however should:

requires:
  PSRule: '@pre >=1.4.0'

This doesn't affect actual execution, but schema validation in VSCode incorrectly shows an error.

Expected behaviour

Allow a space directly after @pre

Module in use and version:

• Module: PSRule
• Version: 1.5.0-B2106006

Captured output from $PSVersionTable:

Name                           Value
----                           -----
PSVersion                      7.1.3
PSEdition                      Core
GitCommitId                    7.1.3
OS                             Microsoft Windows 10.0.19043
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0