fix spelling

Author: robrichard

spec/Section 3 -- Type System.md

@@ -1941,7 +1941,7 @@ inform the executor to delay the execution of the current fragment to indicate
 deprioritization of the current fragment. A query with `@defer` directive will cause
 the request to potentially return multiple responses, where non-deferred data is 
 delivered in the initial response and data deferred is delivered in a subsequent
-response. `@include` and `@skip` take presedence over `@defer`. 
+response. `@include` and `@skip` take precedence over `@defer`. 
 
 ```graphql example
 query myQuery($shouldDefer: Boolean) {
@@ -1967,7 +1967,7 @@ directive @stream(label: String, initialCount: Int!, if: Boolean) on FIELD
 The `@stream` directive may be provided for a field of `List` type so that the 
 backend can leverage technology such as asynchronous iterators to provide a partial
 list in the initial response, and additional list items in subsequent responses.
-`@include` and `@skip` take presedence over `@stream`.
+`@include` and `@skip` take precedence over `@stream`.
 
 ```graphql example
 query myQuery($shouldDefer: Boolean) {