`OpenApiDocument.SecurityRequirements` inconsistently named `SecurityRequirements`, instead of `Security` per the OpenAPI spec

[ravindUwU]

Describe the bug
Extremely nitpicky 😅, but I noticed that the OpenApiDocument property for the security field of the OpenAPI object is named SecurityRequirements, instead of Security.

OpenAPI.NET/src/Microsoft.OpenApi/Models/OpenApiDocument.cs

Lines 73 to 77 in e7c74b8

	/// <summary>
	/// A declaration of which security mechanisms can be used across the API.
	/// </summary>
	public IList<OpenApiSecurityRequirement>? SecurityRequirements { get; set; } =
	new List<OpenApiSecurityRequirement>();

In general, the models & their properties seem to be named after their spec counterparts (but I haven't exhaustively searched for other inconsistencies).

While I wouldn't normally raise issues for issues as minor as this, I thought I'd make this one in this instance because renaming this property would be a breaking change, and v2 is an upcoming major release; so if this is deemed worth fixing, I'd imagine now would be the time for it? (or in v3 hehe). I guess it could also be fixed in a backward-compatible way by renaming the property to Security and adding an [Obsolete] SecurityRequirements => Security?

Expected behavior
Presence of a Security property in OpenApiDocument, but it is named SecurityRequirements instead.

Additional context
The OpenApiOperation property for the security field of the Operation object is named Security, as expected.

OpenAPI.NET/src/Microsoft.OpenApi/Models/OpenApiOperation.cs

Lines 91 to 98 in e7c74b8

	/// <summary>
	/// A declaration of which security mechanisms can be used for this operation.
	/// The list of values includes alternative security requirement objects that can be used.
	/// Only one of the security requirement objects need to be satisfied to authorize a request.
	/// This definition overrides any declared top-level security.
	/// To remove a top-level security declaration, an empty array can be used.
	/// </summary>
	public IList<OpenApiSecurityRequirement>? Security { get; set; } = new List<OpenApiSecurityRequirement>();

[RachitMalik12]

@ravindUwU Apologies for the delay. If you would like to submit this PR to make this fix, we would appreciate it! thanks for catching it!

[ravindUwU]

Thanks @RachitMalik12! I will send a PR with this fix shortly.

Would you mind confirming whether an [Obsolete] SecurityRequirements property that forwards Security is required here; or would a simple rename (and therefore, a breaking change) suffice, because this'll be released in v2?

[baywet]

@ravindUwU thanks for the pull request!
No, a compatibility obsolete property is NOT required here since we'll make that change ONLY in v2 which contains other breaking changes.