doc: Fix the name of the new function

Signed-off-by: Martin Storsjö <martin@martin.st>

doc/APIchanges

@@ -106,7 +106,7 @@ API changes, most recent first:
   Add av_toupper()/av_tolower()
 
 2011-11-05 - b6d08f4 - lavf 53.13.0
-  Add avformat_network_init()/avformat_network_uninit()
+  Add avformat_network_init()/avformat_network_deinit()
 
 2011-10-27 - 512557b - lavc 53.15.0
   Remove avcodec_parse_frame.