release build_web_compilers/build_modules that support Dart 3.1

[jakemac53]

cc @elliette

[github-actions]

Package publishing

Package	Version	Status	Publish tag
package:build_modules	5.0.2	ready to publish (merge and tag to publish)	build_modules-v5.0.2
package:build_web_compilers	4.0.3	ready to publish (merge and tag to publish)	build_web_compilers-v4.0.3
package:build_runner_core	7.2.8-dev	version 7.2.8-dev is pre-release; no publish necessary
package:build_config	1.1.2-dev	version 1.1.2-dev is pre-release; no publish necessary
package:build_daemon	4.0.1-dev	version 4.0.1-dev is pre-release; no publish necessary
package:scratch_space	1.0.2-dev	version 1.0.2-dev is pre-release; no publish necessary
package:build_resolvers	2.2.0	already published at pub.dev
package:build	2.3.2-dev	version 2.3.2-dev is pre-release; no publish necessary
package:build_test	2.1.7	already published at pub.dev
package:build_runner	2.4.1	already published at pub.dev

Documentation at https://github.com/dart-lang/ecosystem/wiki/Publishing-automation.