manual: update gst-controller chapter
manual: update gst-controller chapter

The docs were still describing deprecated api. Update it to tell about
control-cources.

magcius/gstreamer,jpakkane/gstreamer,Lachann/gstreamer,cablelabs/gstreamer,drothlis/gstreamer,drothlis/gstreamer,lovebug356/gstreamer,collects/gstreamer,cfoch/gstreamer,StreamUtils/gstreamer,centricular/gstreamer,cablelabs/gstreamer,krieger-od/gstreamer,StreamUtils/gstreamer,mparis/gstreamer,Distrotech/gstreamer,lubosz/gstreamer,lubosz/gstreamer,surround-io/gstreamer,lubosz/gstreamer,jpakkane/gstreamer,centricular/gstreamer,collects/gstreamer,mparis/gstreamer,collects/gstreamer,magcius/gstreamer,centricular/gstreamer,jpakkane/gstreamer,StreamUtils/gstreamer,mrchapp/gstreamer,ahmedammar/platform_external_gst_gstreamer,jpxiong/gstreamer,shelsonjava/gstreamer,mrchapp/gstreamer,ylatuya/gstreamer,ahmedammar/platform_external_gst_gstreamer,magcius/gstreamer,surround-io/gstreamer,surround-io/gstreamer,ylatuya/gstreamer,jpakkane/gstreamer,ahmedammar/platform_external_gst_gstreamer,justinjoy/gstreamer,krieger-od/gstreamer,centricular/gstreamer,ahmedammar/platform_external_gst_gstreamer,drothlis/gstreamer,jpakkane/gstreamer,mparis/gstreamer,justinjoy/gstreamer,lovebug356/gstreamer,krichter722/gstreamer,mrchapp/gstreamer,cablelabs/gstreamer,ahmedammar/platform_external_gst_gstreamer,krieger-od/gstreamer,surround-io/gstreamer,collects/gstreamer,Lachann/gstreamer,justinjoy/gstreamer,jpxiong/gstreamer,ylatuya/gstreamer,Lachann/gstreamer,shelsonjava/gstreamer,magcius/gstreamer,lubosz/gstreamer,shelsonjava/gstreamer,lovebug356/gstreamer,lovebug356/gstreamer,cablelabs/gstreamer,surround-io/gstreamer,Distrotech/gstreamer,magcius/gstreamer,lovebug356/gstreamer,shelsonjava/gstreamer,ensonic/gstreamer,mparis/gstreamer,Distrotech/gstreamer,krichter722/gstreamer,ensonic/gstreamer,Distrotech/gstreamer,krichter722/gstreamer,centricular/gstreamer,Lachann/gstreamer,shelsonjava/gstreamer,collects/gstreamer,ylatuya/gstreamer,mrchapp/gstreamer,cfoch/gstreamer,jpxiong/gstreamer,krieger-od/gstreamer,mparis/gstreamer,Lachann/gstreamer,drothlis/gstreamer,cfoch/gstreamer,mrchapp/gstreamer,jpxiong/gstreamer,jpxiong/gstreamer,cablelabs/gstreamer,ylatuya/gstreamer,Distrotech/gstreamer,krieger-od/gstreamer,lubosz/gstreamer,krichter722/gstreamer,StreamUtils/gstreamer,cfoch/gstreamer,ensonic/gstreamer,StreamUtils/gstreamer,cfoch/gstreamer,drothlis/gstreamer,justinjoy/gstreamer,justinjoy/gstreamer,krichter722/gstreamer,ensonic/gstreamer,ensonic/gstreamer