Update dependency ergebnis/composer-normalize to v2.21.0

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
ergebnis/composer-normalize	require-dev	minor	2.18.0 -> 2.21.0

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Release Notes

ergebnis/composer-normalize

v2.21.0

Compare Source

For a full diff see [2.20.0...2.21.0][2.20.0...2.21.0].

Changed

• Dropped support for PHP 7.3 ([#​852]), by [@​localheinz]

v2.20.0

Compare Source

For a full diff see [2.19.0...2.20.0][2.19.0...2.20.0].

Changed

• Dropped support for PHP 7.2 ([#​845]), by [@​localheinz]

v2.19.0

Compare Source

For a full diff see [2.18.0...2.19.0][2.18.0...2.19.0].

Changed

• Required composer/composer:2.2.1 for compiling composer-normalize.phar ([#​842]), by [@​localheinz]

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