Update the spec version in the diagnostic object to be more explicit

Author: MaggieKimani1

src/Microsoft.OpenApi.Readers/ParsingContext.cs

@@ -69,7 +69,7 @@ internal OpenApiDocument Parse(YamlDocument yamlDocument)
                 case string version when version.is3_0() || version.is3_1():
                     VersionService = new OpenApiV3VersionService(Diagnostic);
                     doc = VersionService.LoadDocument(RootNode);
-                    this.Diagnostic.SpecificationVersion = OpenApiSpecVersion.OpenApi3_0;
+                    this.Diagnostic.SpecificationVersion = version.is3_1() ? OpenApiSpecVersion.OpenApi3_1 : OpenApiSpecVersion.OpenApi3_0;
                     ValidateRequiredFields(doc, version);
                     break;