Update errata formatting.

docs/errata.html

@@ -199,9 +199,11 @@ o11 = i11 * w00 + i12 * w01 + i13 * w02 +
     <h2>Page 277</h2>
     <p><i>The first code annotation should read:</i></p>
     <p>
-        # In[7]:
-        from p2ch10.vis import findPositiveSamples, showCandidate
-        positiveSample_list = findPositiveSamples()
+<pre>
+# In[7]:
+from p2ch10.vis import findPositiveSamples, showCandidate
+positiveSample_list = findPositiveSamples()
+</pre>
     </p>
 
 </div>