fix: use defined variable for main export

Author: Planeshifter

lib/node_modules/@stdlib/_tools/github/fetch-file/lib/index.js

@@ -71,7 +71,7 @@ var factory = require( './factory.js' );
 
 // MAIN //
 
-setReadOnly( createRepo, 'factory', factory );
+setReadOnly( main, 'factory', factory );
 
 
 // EXPORTS //