Fix: correct doctest output

Author: Payal-Goswami

lib/node_modules/@stdlib/fs/read-file/examples/index.js

@@ -34,7 +34,7 @@ file = readFile.sync( 'beepboop', {
 // returns <Error>
 
 console.log( file instanceof Error );
-// => true
+// => false
 
 /* Async */