Fix get commit function that was returning an array

Change-type: patch
Signed-off-by: Kyle Harding <kyle@balena.io>

src/client.ts

@@ -90,7 +90,7 @@ type Commit = components['schemas']['commit'];
 // https://docs.github.com/en/rest/commits/commits#get-a-commit
 export async function getCommit(context: any, sha: string): Promise<Commit> {
 	const request = context.repo({
-		sha,
+		ref: sha,
 	});
 	const { data: commit } = await context.octokit.rest.repos.getCommit(request);
 	return commit;