TUT: consistent writeCompression option

- Use on/off vs longer compressed/uncompressed.
  For consistency, replaced yes/no with on/off.

- Avoid the combination of binary/compressed,
  which is disallowed and provokes a warning anyhow

tutorials/mesh/foamyHexMesh/blob/system/controlDict

@@ -42,7 +42,7 @@ writeFormat     ascii;
 
 writePrecision  12;
 
-writeCompression uncompressed;
+writeCompression off;
 
 timeFormat      general;