Update dependency @rails/webpacker to v5.4.4

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
@rails/webpacker	5.1.1 -> 5.4.4

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Release Notes

rails/webpacker (@​rails/webpacker)

v5.4.4

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v5.4.3

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• Specify webpack-dev-server to be v3, to avoid getting webpack-dev-server v4 (#​3121)

v5.4.2

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• Fix babel warning about private-methods in @babel/plugin-proposal-private-property-in-object as well (67fa6edf).

v5.4.1

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• Update all dependencies within the same major version (#​3120)
• Fix babel warning about private-methods (#​3016)

v5.4.0

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• Fix compatibility with Psych 4 (ceaf826d)

v5.3.0

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• Adds experimental Yarn 2 support. Note you must manually set nodeLinker: node-modules in your .yarnrc.yml.
• Keep backups, even when they're old #​2912

v5.2.2

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• Bump deps and remove node-sass #​2997.

v5.2.1

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• Revert #​1311.

v5.2.0

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• Bump dependencies and fixes. See diff for changes.

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