Add missing MergeStatus enum member for, cannot_be_merged_recheck.

[tpayne84]

This change adds support for the missing MergeStatus => cannot_be_merged_recheck.

This resolves:

Unhandled exception. System.AggregateException: One or more errors occurred. (Error converting value "cannot_be_merged_recheck" to type 'GitLabApiClient.Models.MergeRequests.Responses.MergeStatus'. Path '[0].merge_status', line 1, position 5331.)
 ---> Newtonsoft.Json.JsonSerializationException: Error converting value "cannot_be_merged_recheck" to type 'GitLabApiClient.Models.MergeRequests.Responses.MergeStatus'. Path '[0].merge_status', line 1, position 5331.
 ---> System.ArgumentException: Requested value 'cannot_be_merged_recheck' was not found.
   at Newtonsoft.Json.Utilities.EnumUtils.ParseEnum(Type enumType, NamingStrategy namingStrategy, String value, Boolean disallowNumber)
   at Newtonsoft.Json.Converters.StringEnumConverter.ReadJson(JsonReader reader, Type objectType, Object existingValue, JsonSerializer serializer)
   --- End of inner exception stack trace ---
   at Newtonsoft.Json.Converters.StringEnumConverter.ReadJson(JsonReader reader, Type objectType, Object existingValue, JsonSerializer serializer)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.DeserializeConvertable(JsonConverter converter, JsonReader reader, Type objectType, Object existingValue)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.SetPropertyValue(JsonProperty property, JsonConverter propertyConverter, JsonContainerContract containerContract, JsonProperty containerProperty, JsonReader reader, Object target)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateObject(Object newObject, JsonReader reader, JsonObjectContract contract, JsonProperty member, String id)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObject(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateList(IList list, JsonReader reader, JsonArrayContract contract, JsonProperty containerProperty, String id)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateList(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, Object existingValue, String id)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
   at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
   at Newtonsoft.Json.JsonSerializer.Deserialize(JsonReader reader, Type objectType)
   at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings)
   at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings)
   at GitLabApiClient.Internal.Http.Serialization.RequestsJsonSerializer.Deserialize[T](String serializeJson)
   at GitLabApiClient.Internal.Http.GitLabApiRequestor.ReadResponse[T](HttpResponseMessage responseMessage)
   at GitLabApiClient.Internal.Http.GitLabApiRequestor.GetWithHeaders[T](String url)
   at GitLabApiClient.Internal.Http.GitLabApiPagedRequestor.GetPagedList[T](String url)
   at GitLabApiClient.MergeRequestsClient.GetAsync(ProjectId projectId, Action`1 options)