docs: mention GstActivateMode rename in porting doc
docs: mention GstActivateMode rename in porting doc

jpxiong/gstreamer,surround-io/gstreamer,collects/gstreamer,mparis/gstreamer,Lachann/gstreamer,collects/gstreamer,Lachann/gstreamer,surround-io/gstreamer,StreamUtils/gstreamer,cablelabs/gstreamer,shelsonjava/gstreamer,ensonic/gstreamer,centricular/gstreamer,krieger-od/gstreamer,cfoch/gstreamer,jpxiong/gstreamer,mparis/gstreamer,krichter722/gstreamer,justinjoy/gstreamer,centricular/gstreamer,krichter722/gstreamer,centricular/gstreamer,mparis/gstreamer,Lachann/gstreamer,mparis/gstreamer,krichter722/gstreamer,cfoch/gstreamer,lovebug356/gstreamer,centricular/gstreamer,ensonic/gstreamer,centricular/gstreamer,lubosz/gstreamer,jpakkane/gstreamer,cablelabs/gstreamer,jpakkane/gstreamer,shelsonjava/gstreamer,ensonic/gstreamer,ensonic/gstreamer,shelsonjava/gstreamer,Lachann/gstreamer,cablelabs/gstreamer,krieger-od/gstreamer,surround-io/gstreamer,StreamUtils/gstreamer,lovebug356/gstreamer,justinjoy/gstreamer,justinjoy/gstreamer,lovebug356/gstreamer,cfoch/gstreamer,jpakkane/gstreamer,jpxiong/gstreamer,lovebug356/gstreamer,krichter722/gstreamer,shelsonjava/gstreamer,lovebug356/gstreamer,lubosz/gstreamer,jpxiong/gstreamer,lubosz/gstreamer,jpakkane/gstreamer,cablelabs/gstreamer,cfoch/gstreamer,StreamUtils/gstreamer,krieger-od/gstreamer,cablelabs/gstreamer,Lachann/gstreamer,shelsonjava/gstreamer,justinjoy/gstreamer,krieger-od/gstreamer,surround-io/gstreamer,collects/gstreamer,lubosz/gstreamer,StreamUtils/gstreamer,krieger-od/gstreamer,StreamUtils/gstreamer,collects/gstreamer,krichter722/gstreamer,mparis/gstreamer,ensonic/gstreamer,justinjoy/gstreamer,lubosz/gstreamer,surround-io/gstreamer,jpxiong/gstreamer,collects/gstreamer,cfoch/gstreamer,jpakkane/gstreamer