[Snyk] Security upgrade alpine from 3.11 to 3.20.3

[WilliamUK17]

Snyk has created this PR to fix 1 vulnerabilities in the dockerfile dependencies of this project.

Keeping your Docker base image up-to-date means you’ll benefit from security fixes in the latest version of your chosen image.

Snyk changed the following file(s):

• slides/Dockerfile

We recommend upgrading to alpine:3.20.3, as this image has only 1 known vulnerabilities. To do this, merge this pull request, then verify your application still works as expected.

Vulnerabilities that will be fixed with an upgrade:

	Issue	Score
	Out-of-bounds Write SNYK-ALPINE311-ZLIB-2977081	714

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Important

• Check the changes in this PR to ensure they won't cause issues with your project.
• Max score is 1000. Note that the real score may have changed since the PR was raised.
• This PR was automatically created by Snyk using the credentials of a real user.

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