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`.

1991/brnstnd/sorta.README.html

@@ -141,7 +141,7 @@ patches.</p>
 [1=D1s&gt;1Ds_+#T=-2/D=1]:1ld [ aux routine for :@ ]ld
 [1D=d2/1=1ddd1 ]:!ld
 [&quot;0&quot;Td]:0ld
-[DD=!1_+=0]:@ld     [ input m, m assumed nonnegative, append 
+[DD=!1_+=0]:@ld     [ input m, m assumed nonnegative, append
           binary representation of m to top of s stack ]ld
 
 [&quot;-&quot;T_]:+ld

1991/brnstnd/sorta.README.md

@@ -31,7 +31,7 @@ This is self-explanatory.
     [1=D1s>1Ds_+#T=-2/D=1]:1ld [ aux routine for :@ ]ld
     [1D=d2/1=1ddd1 ]:!ld
     ["0"Td]:0ld
-    [DD=!1_+=0]:@ld     [ input m, m assumed nonnegative, append 
+    [DD=!1_+=0]:@ld     [ input m, m assumed nonnegative, append
 			  binary representation of m to top of s stack ]ld
 
     ["-"T_]:+ld

1991/westley/README.md

@@ -188,7 +188,7 @@ longer loses games.
 If you want a program that never loses, simply replace the string
 `"9999999999  :-| "` with `"9883857753  :-| "`.
 
-### How it works 
+### How it works
 
 The vertical "bars" of the grid are identical functions, with the name of the
 function as `a()`, `b()`, or `c()`.  After each function is called, the global