rtmp-services: Use "scenecut=0" x264 option for Twitch

This option is an x264-specific feature that may generate additional
keyframes when a major visual change in the output is detected.  This
functionality is undesirable for streaming because it can cause
keyframes to become inconsistent and unpredictable, which can negatively
affect viewer buffering.

plugins/rtmp-services/data/package.json

 {
 	"url": "https://obsproject.com/obs2_update/rtmp-services",
-	"version": 18,
+	"version": 19,
 	"files": [
 		{
 			"name": "services.json",
-			"version": 18
+			"version": 19
 		}
 	]
 }

plugins/rtmp-services/data/services.json

@@ -114,7 +114,8 @@
                 "keyint": 2,
                 "profile": "main",
                 "max video bitrate": 3500,
-                "max audio bitrate": 160
+                "max audio bitrate": 160,
+                "x264opts": "scenecut=0"
             }
         },
         {