Fix continue-as-new handling in workflow_streams subscribe #5451

Job	Run time
cloud-test	2m 3s
check-protos	8m 25s
build-lint-test (3.10, ubuntu-arm)	3m 29s
build-lint-test (3.14, ubuntu-latest)	2m 38s
build-lint-test (3.14, macos-arm)	2m 9s
build-lint-test (3.14, ubuntu-arm)	3m 43s
features-tests / test	8m 29s
build-lint-test (3.10, ubuntu-latest)	2m 9s
build-lint-test (3.10, macos-arm)	3m 30s
test-latest-deps	2m 0s
build-lint-test (3.10, windows-latest)	4m 21s
build-lint-test (3.14, windows-latest)	5m 7s
	48m 3s

Provide feedback