Fix a simple typo. Has this to be fixed also in other branches?

Doc/lib/libzipfile.tex

@@ -97,7 +97,7 @@ cat myzip.zip >> python.exe
   the archive, and should be \constant{ZIP_STORED} or
   \constant{ZIP_DEFLATED}; unrecognized values will cause
   \exception{RuntimeError} to be raised.  If \constant{ZIP_DEFLATED}
-  is specified but the \refmodule{zlib} module is not avaialble,
+  is specified but the \refmodule{zlib} module is not available,
   \exception{RuntimeError} is also raised.  The default is
   \constant{ZIP_STORED}. 
 \end{classdesc}