Updated Texassemble (markdown)

Texassemble.md

@@ -8,7 +8,7 @@ This DirectXTex sample is a command-line texture utility for creating ``DDS`` fi
 ``Texassemble.exe`` uses the following command syntax:
 
 ```
-texassemble <command> [options] [-flist <filename>] <file-name(s)>
+texassemble <command> [options] [--file-list <filename>] <file-name(s)>
 ```
 
 The file-name parameter indicates the file(s) to use to create the assembled image using ``dds``, ``tga``, ``hdr``, or a WIC-supported format (``bmp``, ``jpg``, ``png``, ``jxr``, etc.).