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`.

1989/fubar/README.md

@@ -26,7 +26,7 @@ For more detailed information see [1989 fubar bugs](../../bugs.html#1989_fubar).
 ## Try:
 
 ```sh
-./try.sh # run on 1 - 7 
+./try.sh # run on 1 - 7
 
 ./fubar.sh 2 # run via script
 ./fubar 2 # run directly

1989/fubar/index.html

@@ -149,7 +149,7 @@ href="../../bugs.html#1989_fubar">1989 fubar bugs</a>.</p>
 <h2 id="to-use">To use:</h2>
 <div class="sourceCode" id="cb3"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb3-1"><a href="#cb3-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./fubar</span> <span class="op">&lt;</span>number<span class="op">&gt;</span></span></code></pre></div>
 <h2 id="try">Try:</h2>
-<div class="sourceCode" id="cb4"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb4-1"><a href="#cb4-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./try.sh</span> <span class="co"># run on 1 - 7 </span></span>
+<div class="sourceCode" id="cb4"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb4-1"><a href="#cb4-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./try.sh</span> <span class="co"># run on 1 - 7</span></span>
 <span id="cb4-2"><a href="#cb4-2" aria-hidden="true" tabindex="-1"></a></span>
 <span id="cb4-3"><a href="#cb4-3" aria-hidden="true" tabindex="-1"></a><span class="ex">./fubar.sh</span> 2 <span class="co"># run via script</span></span>
 <span id="cb4-4"><a href="#cb4-4" aria-hidden="true" tabindex="-1"></a><span class="ex">./fubar</span> 2 <span class="co"># run directly</span></span></code></pre></div>