v6.0.0

⚠ BREAKING CHANGES

• typescript@3.7.x introduced some breaking changes in
  generated code.
• require node 10 in engines field (#926)
• remove deprecated methods (#906)

Features

• require node 10 in engines field (#926) (d89c59a)

Bug Fixes

• do not warn for SDK creds (#905) (9536840)
• use iamcredentials API to sign blobs (#908) (7b8e4c5)
• deps: update dependency gaxios to v3 (#917) (1f4bf61)
• deps: update dependency gcp-metadata to v4 (#918) (d337131)
• types: add additional fields to TokenInfo (#907) (5b48eb8)

Build System

• update to latest gts and TypeScript (#927) (e11e18c)

Miscellaneous Chores

• remove deprecated methods (#906) (f453fb7)