fix: update execa dependency to 2.1.0

[Trott]

This PR contains:

• bugfix
• feature
• refactor
• tests
• documentation
• metadata

Breaking Changes?

• yes
• no

If yes, please describe the breakage.

Please Describe Your Changes

Update execa dependency to 2.1.0 in package-lock.json. Without this
change, tests will fail when run with Node.js 13.x-pre and may fail when
13.0.0 is released in 13 days.

Refs: sindresorhus/execa#370

[codecov-io]

Codecov Report

Merging #147 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #147   +/-   ##
=======================================
  Coverage   97.24%   97.24%           
=======================================
  Files           1        1           
  Lines         145      145           
=======================================
  Hits          141      141           
  Misses          4        4

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d221504...15f0d7b. Read the comment docs.

[shellscape]

Thanks for this PR 🍺

[Trott]

I know it's just a test fix, but any chance I can persuade you to publish a new release? There seem to be some legitimate bug fixes since the last release, so it wouldn't be a complete no-change release for end users. This particular fix will help Node.js's ecosystem-testing tool CITGM, which downloads a tarball of the latest release and runs tests. So CITGM won't use this fix until it's part of a release.