remove trailing blanks in markdown files

We used this command to find markdown files with trailing whitespace.

```sh
find . -name '*.md' -print0 | xargs -0 grep -E -l '[[:space:]][[:space:]]*$'
```

After removal, we did a `make www`.

1993/rince/design.html

@@ -130,9 +130,9 @@ system, with some of the transitions bound to key presses.</p>
 off a hill <code>/</code> A standard automata would have 2 rules
 something like this:</p>
 <pre><code>
-        o..         ...   
-        \..  --&gt;  &#39;o&#39;       .o.  --&gt;  &#39;.&#39;    
-        ...         .\.   </code></pre>
+        o..         ...
+        \..  --&gt;  &#39;o&#39;       .o.  --&gt;  &#39;.&#39;
+        ...         .\.</code></pre>
 <p>However, the system I devised, in order to keep things small and
 neat(!), was to define a 3x3 to 3x3 map (instead of the 3x3 to 1x1 shown
 above). Hence:</p>

1993/rince/design.md

@@ -11,9 +11,9 @@ A standard automata would have 2 rules something like this:
 
 ```
 
-		o..			...	  
-		\..  -->  'o'		.o.  -->  '.'    
-		...			.\.   
+		o..			...
+		\..  -->  'o'		.o.  -->  '.'
+		...			.\.
 ```
 
 However, the system I devised, in order to keep things small and neat(!),