Fix spacing in ES.63 example (#1351)

CppCoreGuidelines.md

@@ -12110,7 +12110,7 @@ In the rare cases where the slicing was deliberate the code can be surprising.
     Circle c2 {{1, 1}, 43};
     assign(c, c2);   // oops, not the whole state is transferred
     assert(c == c2); // if we supply copying, we should also provide comparison,
-                      //   but this will likely return false
+                     // but this will likely return false
 
 The result will be meaningless because the center and radius will not be copied from `c` into `s`.
 The first defense against this is to [define the base class `Shape` not to allow this](#Rc-copy-virtual).