deps: upgrade npm to 7.21.1

v7.21.1 (2021-08-26)

BUG FIXES

• 4e52217cb #3684 fix(config): respect --global, --package-lock-only (@nlf)

DEPENDENCIES

• e3878536f make-fetch-happen@9.1.0:
  • fix: use the same strictSSL default as tls.connect
• 145f70cc1 read-package-json@4.0.1:
  • fix: Add gitHead in subdirectories too
  • fix(man): don't resolve paths to man files
• 3f4d37143 tar@6.1.11:
  • fix: perf regression on hot string munging path
• e63a942c6 cacache@15.3.0:
  • feat: introduce @npmcli/fs for tmp dir methods

DOCUMENTATION

• 957fa6040 #3681 clarify uninstall lifecycle script (@fritzy)