lptsinkbin: Disable sync property at appsink
lptsinkbin: Disable sync property at appsink

For text data handling, sync property is disabled at appsink.
After apply this patch, appsink will throw data immediately to upper layer
when it receive the data.

:issues addressed:
[GF-55091][GFP2TestPass] Smartshare - Close Captioning is not working.

Change-Id: I00ac7a9066f82dee4785fa3ddf24450f191ce4be
Reviewed-on: https://gpro.palm.com/24026
Reviewed-by: Jeongseok Kim <0c03ab7a1b32f29697716389c3f9549845834271@lge.com>
Tested-by: Jeongseok Kim <0c03ab7a1b32f29697716389c3f9549845834271@lge.com>

justinjoy/gst-plugins-lp,justinjoy/gst-plugins-lp