release.yml: use correct target_commitish arg

Use the correct name for setting the target of a tag in the release
workflow, for creating a draft release.

Author: mjcheetham

.github/workflows/release.yml

@@ -749,7 +749,7 @@ jobs:
               ...releaseMetadata,
               draft: true,
               tag_name: tagName,
-              tag_commitish: context.sha,
+              target_commitish: context.sha,
               name: `GCM ${version}`
             });
             releaseMetadata.release_id = createdRelease.data.id;