Style fix

docs/src/guide/boundaries.md

@@ -103,7 +103,7 @@ only for frequency domain driven simulations.
     computational domain and instead must exist only on the outer boundary of the domain
     (they are to be  "one-sided" in the sense that mesh elements only exist on one side of
     the boundary).
-
+    
     Wave ports are not currently compatible with nonconformal mesh refinement.
 
 The incident field excitation at a lumped or wave port is controlled by setting