Adds missing "transfer full" annotation for caps parameter in
gst_pad_template_set_documentation_caps()
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/648>
/**
* gst_pad_template_set_documentation_caps:
* @templ: the pad template to set documented capabilities on
- * @caps: the documented capabilities
+ * @caps: (transfer full): the documented capabilities
*
* Certain elements will dynamically construct the caps of their
* pad templates. In order not to let environment-specific information