Fix it's vs its typo (#255)

Co-authored-by: Thomer Gil <[email protected]>

README.md

@@ -180,7 +180,7 @@ $ modprobe bcm2835-v4l2 max_video_width=2592 max_video_height=1944
 µStreamer supports bandwidth-efficient streaming using [H.264 compression](https://en.wikipedia.org/wiki/Advanced_Video_Coding) and the Janus WebRTC server. See the [Janus integration guide](docs/h264.md) for full details.
 
 ## Nginx
-When uStreamer is behind an Nginx proxy, it's buffering behavior introduces latency into the video stream. It's possible to disable Nginx's buffering to eliminate the additional latency:
+When uStreamer is behind an Nginx proxy, its buffering behavior introduces latency into the video stream. It's possible to disable Nginx's buffering to eliminate the additional latency:
 
 ```nginx
 location /stream {