Bump docker/build-push-action from 3 to 6 #182

Job	Run time
Linting	2m 1s
Build for Windows (windows, amd64)	1m 15s
Build for Linux (linux, amd64)	1m 13s
Unit tests	3m 45s
WASM build test	0s
Build for Linux (linux, 386)	1m 23s
Initial tests passed	3s
Sytest (SQLite native)	4m 38s
Upgrade tests from HEAD-2	7m 10s
Sytest (SQLite Cgo)	4m 42s
Integration tests	4m 58s
Complement (SQLite native)	4m 37s
Sytest (PostgreSQL)	5m 58s
Complement (SQLite Cgo)	4m 45s
Upgrade tests	7m 20s
Complement (PostgreSQL)	9m 32s
Integration tests passed	2s
Update Docker images	0s
	1h 3m 22s

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