chore(deps): update dependency rollup to v2.51.1

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
rollup (source)	2.51.0 -> 2.51.1

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Release Notes

rollup/rollup

### [`v2.51.1`](https://togithub.com/rollup/rollup/blob/master/CHANGELOG.md#​2511) [Compare Source](https://togithub.com/rollup/rollup/compare/v2.51.0...v2.51.1) *2021-06-08* ##### Bug Fixes - Fix error when using `defineConfig` ([#​4134](https://togithub.com/rollup/rollup/issues/4134)) ##### Pull Requests - [#​4134](https://togithub.com/rollup/rollup/pull/4134): export `rollup.defineConfig` at runtime ([@​mshrtsr](https://togithub.com/mshrtsr))

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