chore: rev etcd to 3.3.18

[mboersma]

Reason for Change:
See https://github.com/etcd-io/etcd/releases/tag/v3.3.18

Issue Fixed:
Fixes #2404

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Notes:

[jackfrancis]

/lgtm

[acs-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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[codecov]

Codecov Report

Merging #2462 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2462   +/-   ##
=======================================
  Coverage   72.58%   72.58%           
=======================================
  Files         130      130           
  Lines       23889    23889           
=======================================
  Hits        17339    17339           
  Misses       5524     5524           
  Partials     1026     1026