deps: update npm to 5.7.1

[FallenRiteMonk]

Fixes: #19271

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

[MylesBorins]

@FallenRiteMonk did you follow https://github.com/nodejs/node/blob/master/doc/guides/maintaining-npm.md when doing this?

[MylesBorins]

We will need #19293 to land first in order to run the test suite

We also may want to hold off on upgrading to the 5.7 line until the publishing epoch time bug is fixed

npm/npm#19968

(5.7.0 suffered from another regression as well)

[FallenRiteMonk]

@MylesBorins no I did not follow this guide (didn't see it).
Will close this and reopen a new one following the guide once the two issues are resolved