fixed missing spaces in tutorial

doc/tutorial.rst

@@ -558,10 +558,10 @@ relation to loop nesting. For example, it's perfectly possible to request
     >>> evt, (out,) = knl(queue, a=x_vec_dev)
     #define lid(N) ((int) get_local_id(N))
     ...
-       for (int i_inner = 0; i_inner <= 15; ++i_inner)
-         if (-1 + -1 * i_inner + n >= 0)
-           for (int i_outer = 0; i_outer <= -1 + -1 * i_inner + ((15 + n + 15 * i_inner) / 16); ++i_outer)
-             a[16 * i_outer + i_inner] = 0.0f;
+      for (int i_inner = 0; i_inner <= 15; ++i_inner)
+        if (-1 + -1 * i_inner + n >= 0)
+          for (int i_outer = 0; i_outer <= -1 + -1 * i_inner + ((15 + n + 15 * i_inner) / 16); ++i_outer)
+            a[16 * i_outer + i_inner] = 0.0f;
     ...
 
 Notice how loopy has automatically generated guard conditionals to make