tools: update extend to 3.0.2

Update `extend` to 3.0.2 as 3.0.1 is susceptible to a low-severity
security issue.

Refs: https://snyk.io/vuln/npm:extend:20180424

PR-URL: #26392
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Masashi Hirano <shisama07@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Author: Trott