✏️ Fix typo in unit tests

I mean, kind of an easy mistake to make, but...

Author: Lamparter

Octokit.GraphQL.Core.UnitTests/ExpressionRewiterTests.cs

@@ -9,9 +9,9 @@
 
 namespace Octokit.GraphQL.Core.UnitTests
 {
-    public class ExpressionRewiterTests
+    public class ExpressionRewriterTests
     {
-        public ExpressionRewiterTests()
+        public ExpressionRewriterTests()
         {
             ExpressionCompiler.IsUnitTesting = true;
         }

Octokit.GraphQL.UnitTests/ExpressionRewiterTests.cs

@@ -11,9 +11,9 @@
 
 namespace Octokit.GraphQL.UnitTests
 {
-    public class ExpressionRewiterTests
+    public class ExpressionRewriterTests
     {
-        public ExpressionRewiterTests()
+        public ExpressionRewriterTests()
         {
             ExpressionCompiler.IsUnitTesting = true;
         }