fix typo

_episodes/03-plotting.md

@@ -525,7 +525,7 @@ x = np.linspace(0, 2, 4)
 > >
 > > Notice also that as the values of `X` become larger,
 > > the number of samples is not enough
-> > and visual artifacts start to appear in. the `sine-cubic` plot.
+> > and visual artifacts start to be noticeable in the `sine-cubic` plot.
 > {: .solution }
 {: .challenge }