Update strmreader read2.cs

.NET source code clearly shows Read() may not return a fixed number of characters, but only what's currently available on the stream. ReadBlock returns the stated number of characters and only returns fewer if end of stream

Author: jontho-microsoft-com

snippets/csharp/System.IO/StreamReader/Read/strmreader read2.cs

@@ -32,7 +32,7 @@ public static void Main()
                 while (sr.Peek() >= 0)
                 {
                     c = new char[5];
-                    sr.Read(c, 0, c.Length);
+                    sr.ReadBlock(c, 0, c.Length);
                     //The output will look odd, because
                     //only five characters are read at a time.
                     Console.WriteLine(c);