Update API interface

Author: MaggieKimani1

test/Microsoft.OpenApi.Tests/PublicApi/PublicApi.approved.txt

@@ -496,6 +496,7 @@ namespace Microsoft.OpenApi.Models
         public const string PathItems = "pathItems";
         public const string Paths = "paths";
         public const string Pattern = "pattern";
+        public const string PatternProperties = "patternProperties";
         public const string Post = "post";
         public const string Prefix = "prefix";
         public const string Produces = "produces";