Fix Typo in Tutorial Project (#931)

* fix typo

* fix typo

Author: liboz

csharp/tutorials/AsyncStreams/finished/IssuePRreport/IssuePRreport/Program.cs

@@ -51,7 +51,7 @@ static async Task Main(string[] args)
             // - public_repo
             // Replace the 3rd parameter to the following code with your GitHub access token.
             var key = GetEnvVariable("GitHubKey",
-            "You must store you GitHub key in the 'GitHubKey' environment variable",
+            "You must store your GitHub key in the 'GitHubKey' environment variable",
             "");
 
             var client = new GitHubClient(new Octokit.ProductHeaderValue("IssueQueryDemo"))

csharp/tutorials/AsyncStreams/start/IssuePRreport/IssuePRreport/Program.cs

@@ -61,7 +61,7 @@ static async Task Main(string[] args)
             // - public_repo
             // Replace the 3rd parameter to the following code with your GitHub access token.
             var key = GetEnvVariable("GitHubKey",
-            "You must store you GitHub key in the 'GitHubKey' environment variable",
+            "You must store your GitHub key in the 'GitHubKey' environment variable",
             "");
 
             var client = new GitHubClient(new Octokit.ProductHeaderValue("IssueQueryDemo"))