Tab width should always be the configured indentation width

`tab_width()` should return the configured indentation width to
appear visually as the correct size regardless of the mode's
configured indentation unit.

This resolves the issue were tabs appear as single width character
rather the configured indentation width in modes who's indentation
unit is spaces.

zee-grammar/src/config.rs

@@ -45,10 +45,7 @@ impl IndentationConfig {
     }
 
     pub fn tab_width(&self) -> usize {
-        match self.unit {
-            IndentationUnit::Space => 1,
-            IndentationUnit::Tab => self.width,
-        }
+        self.width
     }
 }