Fix formatting in exercise 99

The non-conforming formatting was not detected by the eowyn.sh script,
due to a bug.

exercises/099_formatting.zig

@@ -82,7 +82,7 @@
 //
 //      X |  1   2   3   4   5  ...
 //     ---+---+---+---+---+---+
-//      1 |  1   2   3   4   5 
+//      1 |  1   2   3   4   5
 //
 //      2 |  2   4   6   8  10
 //