carlos / platform Public

appconfig: fix main's gate after the relay merge

One-line test fix. Commit 8e16153 (multi-upstream exec routes) added a SyncExec caller in syncexec_test.go; the relay branch (merged as 4316089) gave SyncExec an eighth ack parameter. Each branch was green against its own base; main's gate failed on go vet. Passes nil, the no-ack value every other test uses. No behaviour change.