Build/Test Tools: Update npm lockfile to version 3.

This updates the `package-lock.json` file to use the version 3 format.

Version 3 removes the version 1 format data, resulting in a smaller file. While version 3 format is not supported in npm < 7, a lower limit is enforced in the `engines` declaration within `package.json` and has been >= 7 since [56378].

The Gutenberg repository has already been updated to use version 3.

Props jonsurrell.
See #62190.

git-svn-id: https://develop.svn.wordpress.org/trunk@59206 602fd350-edb4-49c9-b593-d223f7449a82

.npmrc

@@ -1,3 +1,4 @@
-save-exact = true
 engine-strict = true
 legacy-peer-deps = true
+lockfile-version = 3
+save-exact = true