improve layout of 1993/vanb/index.html

Improved indenting of information in a code block.

Ran `bin/readme2index.sh -v 1 1993/vanb` to perform the above.

1993/vanb/README.md

@@ -42,9 +42,9 @@ The octal expression may contain:
 ```
     unary operators:	+, -
     binary operators	+, -, *, /, %
-    hex numbers:		x or X followed by hex digits
+    hex numbers:	x or X followed by hex digits
     decimal numbers:	d or D followed by decimal digits
-    octal numbers:		octal digits
+    octal numbers:	octal digits
     grouping:		()
 ```
 

1993/vanb/index.html

@@ -169,9 +169,9 @@ hexadecimal and decimal numbers.</p>
 <p>The octal expression may contain:</p>
 <pre><code>    unary operators:    +, -
     binary operators    +, -, *, /, %
-    hex numbers:                x or X followed by hex digits
+    hex numbers:        x or X followed by hex digits
     decimal numbers:    d or D followed by decimal digits
-    octal numbers:              octal digits
+    octal numbers:      octal digits
     grouping:           ()</code></pre>
 <p>No spaces are allowed in the expression. To avoid shell expansion,
 one should surround the expression in single quotes.</p>