Typo: "that" --> "than"

This closes SF bug #425320.

Doc/api/api.tex

@@ -55,7 +55,7 @@ Writing an extension module is a relatively well-understood process,
 where a ``cookbook'' approach works well.  There are several tools 
 that automate the process to some extent.  While people have embedded 
 Python in other applications since its early existence, the process of 
-embedding Python is less straightforward that writing an extension.  
+embedding Python is less straightforward than writing an extension.  
 
 Many API functions are useful independent of whether you're embedding 
 or extending Python; moreover, most applications that embed Python