chore(deps): update dependency rollup to v2.56.0

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
rollup (source)	2.55.1 -> 2.56.0

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Release Notes

rollup/rollup

### [`v2.56.0`](https://togithub.com/rollup/rollup/blob/master/CHANGELOG.md#​2560) [Compare Source](https://togithub.com/rollup/rollup/compare/v2.55.1...v2.56.0) *2021-08-05* ##### Features - Create more efficient code for SystemJS exports ([#​4199](https://togithub.com/rollup/rollup/issues/4199)) - Extend `maxParallelFileReads` option to also throttle plugin load hooks ([#​4200](https://togithub.com/rollup/rollup/issues/4200)) ##### Bug Fixes - Return correct value for postfix update expressions of exported variables ([#​4194](https://togithub.com/rollup/rollup/issues/4194)) ##### Pull Requests - [#​4199](https://togithub.com/rollup/rollup/pull/4199): Refine SystemJS export rendering ([@​lukastaegert](https://togithub.com/lukastaegert)) - [#​4200](https://togithub.com/rollup/rollup/pull/4200): Restrict parallel execution of load hook ([@​schummar](https://togithub.com/schummar))

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