migrate-with-more-columns-downstream.md: dmctl option table says -master-addr but examples use --master-addr

What is affected

migrate-with-more-columns-downstream.md (English source, release-8.5 branch and likely master).

The option-reference table documents the flag as a single dash:

| -master-addr | Specifies ${advertise-addr} of any DM-master node in the cluster where dmctl is to be connected. ... |

But every example command in the same file uses a double dash:

tiup dmctl --master-addr ${advertise-addr} binlog-schema update -s ${source-id} ${task-name} ${database-name} ${table-name} ${schema-file}
tiup dmctl --master-addr 172.16.10.71:8261 binlog-schema update -s mysql-01 task-test -d log -t message log.message.sql
tiup dmctl --master-addr ${advertise-addr} resume-task ${task-name}
tiup dmctl --master-addr ${advertise-addr} query-status ${task-name}

A reader who copies the flag name straight from the reference table (-master-addr) instead of the example commands could hit an invalid-flag error, since dmctl expects --master-addr (double dash).

Suggested fix

Correct the table row to `--master-addr` (double dash) to match every example command in the file.

Context

Found while reviewing CodeRabbit feedback on a Japanese translation PR (pingcap/docs#23635) — the JA translation faithfully mirrors this same single-dash/double-dash inconsistency from the EN source, so per this repo's translation convention the fix belongs here in the EN source, not in the JA-only PR.

Open migrate-with-more-columns-downstream.md on the release-8.5 branch and compare the option-reference table with the listed dmctl examples. Update the table entry from -master-addr to --master-addr, then verify that it matches every example in the file.