Update custom-resources.md

Removes extraneous 'with'.

Author: CharlieTLe

content/en/docs/concepts/extend-kubernetes/api-extension/custom-resources.md

@@ -325,7 +325,7 @@ selectable fields.
 
 {{% code_sample file="customresourcedefinition/shirt-resource-definition.yaml" %}}
 
-Field selectors can then be used to get only resources with with a `color` of `blue`:
+Field selectors can then be used to get only resources with a `color` of `blue`:
 
 ```shell
 kubectl get shirts.stable.example.com --field-selector spec.color=blue