[Snyk] Security upgrade alpine from 3.18 to 3 (#1088)

* fix: extras/docker/alpine3.18/Dockerfile to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-6152404
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-6152404
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-6160000
- https://snyk.io/vuln/SNYK-ALPINE318-OPENSSL-6160000



* Change all references to Alpine 3.18 to Alpine 3

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Co-authored-by: snyk-bot <snyk-bot@snyk.io>
Co-authored-by: Ezra Chung <ezra.chung@mongodb.com>