Migration schema nullable column set `null` explicitly #4287

Job	Run time
Rustfmt	17s
Init	3s
Examples (examples/actix_example)	2m 27s
Unit Test	3m 10s
Examples (examples/axum_example)	2m 18s
Clippy	1m 15s
Examples (examples/basic)	1m 1s
Examples (examples/graphql_example)	2m 35s
Examples (examples/jsonrpsee_example)	2m 30s
Examples (examples/loco_example)	3m 12s
Examples (examples/loco_starter)	3m 15s
Examples (examples/poem_example)	2m 22s
Examples (examples/proxy_gluesql_example)	1m 14s
Examples (examples/rocket_example)	3m 0s
Examples (examples/rocket_okapi_example)	3m 18s
Examples (examples/salvo_example)	2m 44s
Examples (examples/seaography_example)	2m 33s
Examples (examples/tonic_example)	2m 25s
Compile SQLite (async-std, native-tls)	2m 50s
Compile PostgreSQL (tokio, native-tls)	2m 51s
Compile MySQL (actix, native-tls)	2m 45s
CLI	0s
Compile PostgreSQL (tokio, rustls)	2m 52s
Compile MySQL (actix, rustls)	2m 45s
Compile SQLite (async-std, rustls)	2m 50s
Issues Matrix	0s
Issues	0s
MySQL (8, actix, native-tls)	3m 18s
MySQL (5.7, actix, native-tls)	3m 37s
MariaDB (10.6, actix, native-tls)	2m 14s
Postgres (14, tokio, native-tls)	6m 43s
Postgres (15, tokio, native-tls)	6m 42s
Postgres (16, tokio, native-tls)	6m 41s
SQLite (async-std, native-tls)	4m 25s
SQLite (async-std, rustls)	4m 22s
	1h 34m 34s

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