release-26.3: ccl/changefeedccl: TestChangefeedProtectedTimestampUpdate failed

ccl/changefeedccl.TestChangefeedProtectedTimestampUpdate [failed](https://mesolite.cluster.engflow.com/invocations/default/427e6fdf-673b-4189-80e1-9670591b3f17?testReportRun=6&testReportShard=15&testReportAttempt=1#targets-Ly9wa2cvY2NsL2NoYW5nZWZlZWRjY2w6Y2hhbmdlZmVlZGNjbF90ZXN0) on release-26.3 @ [2b072437419a9db59bc4307df67890a6b6fbbd7e](https://github.com/cockroachdb/cockroach/commits/2b072437419a9db59bc4307df67890a6b6fbbd7e):

```
=== RUN TestChangefeedProtectedTimestampUpdate
test_log_scope.go:172: test logs captured to: outputs.zip/logTestChangefeedProtectedTimestampUpdate1535305623
test_log_scope.go:82: use -show-logs to present logs inline
changefeed_test.go:13057: -- test log scope end --
test logs left over in: outputs.zip/logTestChangefeedProtectedTimestampUpdate1535305623
--- FAIL: TestChangefeedProtectedTimestampUpdate (6.28s)
=== RUN TestChangefeedProtectedTimestampUpdate/kafka
helpers_test.go:1578: making server as system tenant
test_server_shim.go:639: DRPC is enabled (via testserver factory defaults)
helpers_test.go:1654: making kafka feed factory
changefeed_test.go:13044:
Error Trace: pkg/ccl/changefeedccl/changefeed_test.go:13044
pkg/ccl/changefeedccl/helpers_test.go:1840
pkg/ccl/changefeedccl/helpers_test.go:1876
Error: "1" is not greater than or equal to "2"
Test: TestChangefeedProtectedTimestampUpdate/kafka
--- FAIL: TestChangefeedProtectedTimestampUpdate/kafka (6.28s)
```

Parameters:
- attempt=1
- run=6
- shard=15
Help

See also: [How To Investigate a Go Test Failure \(internal\)](https://cockroachlabs.atlassian.net/l/c/HgfXfJgM)

/cc @cockroachlabs/cdc

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Jira issue: CRDB-66637

Start with pkg/ccl/changefeedccl/changefeed_test.go:13044 and TestChangefeedProtectedTimestampUpdate, then inspect helpers_test.go:1840 and :1876 and the captured test logs. Reproduce the kafka subtest on release-26.3 at commit 2b072437419a9db59bc4307df67890a6b6fbbd7e; done means the test no longer fails its >=2 assertion.

Written by the indexing model from the issue text.