Update dependency rollup to v1.19.4

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
rollup	devDependencies	patch	1.19.3 -> 1.19.4

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Release Notes

rollup/rollup

### [`v1.19.4`](https://togithub.com/rollup/rollup/blob/master/CHANGELOG.md#​1194) [Compare Source](https://togithub.com/rollup/rollup/compare/v1.19.3...v1.19.4) _2019-08-07_ ##### Bug Fixes - Prevent invalid code when exporting an external namespace ([#​3034](https://togithub.com/rollup/rollup/issues/3034)) - Prevent invalid or non-equivalent code when simplifying expressions in return and throw statements ([#​3035](https://togithub.com/rollup/rollup/issues/3035)) ##### Pull Requests - [#​3034](https://togithub.com/rollup/rollup/pull/3034): Avoid generating .\* as export ([@​LongTengDao](https://togithub.com/LongTengDao)) - [#​3035](https://togithub.com/rollup/rollup/pull/3035): Prevent ASI errors for conditional expressions ([@​lukastaegert](https://togithub.com/lukastaegert)) - [#​3036](https://togithub.com/rollup/rollup/pull/3036): Fix documents to use https, not http ([@​giraffate](https://togithub.com/giraffate))

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