Backport of "context: fix transfer annotation on gst_context_writable_structure" into 1.20
requested to merge tpm/gstreamer:backport-mr-1663-into-1.20-fix-gst-context-transfer-annotation into 1.20
Backport of !1663 (merged) "context: fix transfer annotation on gst_context_writable_structure".
Commits:
- fbbeee1d context: fix transfer annotation