chore(deps): update dependency @types/node to v10.12.21

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change	References
@​types/node	devDependencies	patch	10.12.18 -> 10.12.21	source

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[coveralls]

Coverage remained the same at 100.0% when pulling 1ca10a01b59b24de98268e1057d0cad67acaddc8 on renovate/node-10.x into 1e90ffced0665e168dde6af3f29c5693e6bf92f7 on master.