ggwave : remove unused ampl i16 Tx buffer

examples/ggwave-common-sdl2.cpp

@@ -222,7 +222,8 @@ bool GGWave_init(
             GGWave::kDefaultSoundMarkerThreshold,
             sampleFormatInp,
             sampleFormatOut,
-            GGWAVE_OPERATING_MODE_BOTH_RX_AND_TX});
+            (GGWave::OperatingMode) (GGWAVE_OPERATING_MODE_RX | GGWAVE_OPERATING_MODE_TX),
+        });
     }
 
     return true;