chore(library): use schema contains constants in readers

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: baywet

src/Microsoft.OpenApi/Reader/V31/OpenApiSchemaDeserializer.cs

@@ -149,11 +149,11 @@ internal static partial class OpenApiV31Deserializer
             }
         },
         {
-            "contains",
+            OpenApiConstants.Contains,
             (o, n, doc, c) => o.Contains = LoadSchema(n, doc, c)
         },
         {
-            "maxContains",
+            OpenApiConstants.MaxContains,
             (o, n, _, _) =>
             {
                 var maxContains = n.GetScalarValue();
@@ -164,7 +164,7 @@ internal static partial class OpenApiV31Deserializer
             }
         },
         {
-            "minContains",
+            OpenApiConstants.MinContains,
             (o, n, _, _) =>
             {
                 var minContains = n.GetScalarValue();

src/Microsoft.OpenApi/Reader/V32/OpenApiSchemaDeserializer.cs

@@ -149,11 +149,11 @@ internal static partial class OpenApiV32Deserializer
             }
         },
         {
-            "contains",
+            OpenApiConstants.Contains,
             (o, n, doc, c) => o.Contains = LoadSchema(n, doc, c)
         },
         {
-            "maxContains",
+            OpenApiConstants.MaxContains,
             (o, n, _, _) =>
             {
                 var maxContains = n.GetScalarValue();
@@ -164,7 +164,7 @@ internal static partial class OpenApiV32Deserializer
             }
         },
         {
-            "minContains",
+            OpenApiConstants.MinContains,
             (o, n, _, _) =>
             {
                 var minContains = n.GetScalarValue();