Don't update time when added speech

This causes problems when the slow time spell is active as the
time drift calculation sometimes causes the game time to move backwards.
Thanks to bsxf47 for tracking this down.

As far as I can tell, this call is not needed for anything.

See: issue #874

src/gui/Speech.cpp

@@ -343,7 +343,6 @@ long ARX_SPEECH_AddSpeech(Entity * io, const std::string & data, long mood,
 	}
 
 	aspeech[num].exist = 1;
-	arxtime.update();
 	aspeech[num].time_creation = arxtime.now();
 	aspeech[num].io = io; // can be NULL
 	aspeech[num].duration = ArxDurationMs(2000); // Minimum value