Increase HttpClient Timeout in bootstrap script (#4659)

* Increase HttpClient Timeout in bootstrap script

* Update dotnet-install.ps1

Fix comment

scripts/obtain/dotnet-install.ps1

@@ -144,7 +144,9 @@ function GetHTTPResponse([Uri] $Uri)
         else {
             $HttpClient = New-Object System.Net.Http.HttpClient
         }
-
+        # Default timeout for HttpClient is 100s.  For a 50 MB download this assumes 500 KB/s average, any less will time out
+        # 5 minutes allows it to work over much slower connections.
+        $HttpClient.Timeout = New-TimeSpan -Minutes 5 
         $Response = $HttpClient.GetAsync($Uri).Result
         if (($Response -eq $null) -or (-not ($Response.IsSuccessStatusCode)))
         {