Deduplicate scope names in openapi spec generation

[EraYaN]

Clear and concise description of the problem

When you have multiple flows in an OAuth2Auth object with scopes this results in duplicate scopes in the generated openapi.yaml

Like so

security:
  - oauth:
    - api:read
    - api:read

with the tsp as follows:

model oauth<Scopes extends string[]>
  is OAuth2Auth<
    [
      {
        type: OAuth2FlowType.authorizationCode;
        authorizationUrl: "https://example.org/oauth2/v2.0/authorize";
        tokenUrl: "https://example.org/oauth2/v2.0/token";
        refreshUrl: "https://example.org/oauth2/v2.0/token";
      },
      {
        type: OAuth2FlowType.clientCredentials;
        tokenUrl: "https://example.org/oauth2/v2.0/token";
      }
    ],
    Scopes
  >;

model Get200Response {
  @statusCode statusCode: 200;
  @bodyRoot body: int64;
}

@route("/example")
@get
@useAuth(oauth<["api:read"]>)
op Get(): Get200Response

I'd like it if they were de-duplicated since this also results in them showing up twice or even more times in the generated documentation.

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