build: Change alpine image to one compatible with Prisma

[emrysal]

What does this PR do?

Alpine Linux 3.21 isn't compatible with Prisma at this point in time, so reverting the image to the previous 3.20 version.

prisma/prisma#25817

[github-actions]

Hey there and thank you for opening this pull request! 👋🏼

We require pull request titles to follow the Conventional Commits specification and it looks like your proposed title needs to be adjusted.

Details:

No release type found in pull request title "Change alpine image to one compatible with Prisma". Add a prefix to indicate what kind of release this pull request corresponds to. For reference, see https://www.conventionalcommits.org/

Available types:
 - feat: A new feature
 - fix: A bug fix
 - docs: Documentation only changes
 - style: Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc)
 - refactor: A code change that neither fixes a bug nor adds a feature
 - perf: A code change that improves performance
 - test: Adding missing tests or correcting existing tests
 - build: Changes that affect the build system or external dependencies (example scopes: gulp, broccoli, npm)
 - ci: Changes to our CI configuration files and scripts (example scopes: Travis, Circle, BrowserStack, SauceLabs)
 - chore: Other changes that don't modify src or test files
 - revert: Reverts a previous commit

[graphite-app]

Graphite Automations

"Add foundation team as reviewer" took an action on this PR • (12/10/24)

1 reviewer was added to this PR based on Keith Williams's automation.

"Add ready-for-e2e label" took an action on this PR • (12/10/24)

1 label was added to this PR based on Keith Williams's automation.

[github-actions]

E2E results are ready!

• Workflow #40724.1 latest results