gstpad: Fix typo in docstring
gstpad: Fix typo in docstring

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