Update dependency core-js to ^3.4.0

Created by: renovate[bot]

This PR contains the following updates:

Package	Type	Update	New value	References	Sourcegraph
core-js	dependencies	minor	^3.4.0	source

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Release Notes

zloirock/core-js

v3.4.0

Compare Source

• Added well-formed JSON.stringify, ES2019 feature, thanks @​ExE-Boss and @​WebReflection for the idea
• Fixed Math.signbit, #​687, thanks @​chicoxyzzy

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