add vtadmin web files to all lite images

[deepthi]

Description

In #9405 we added vtadmin web files (not binaries) to only the mysql57 version of vitess/lite. This PR adds them to all flavors of the lite image.

Related Issue(s)

#9405 #10543

Checklist

• "Backport me!" label has been added if this change should be backported
• Tests were added or are not required
• Documentation was added or is not required

Deployment Notes

[github-actions]

Review Checklist

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General

• If this is a change that users need to know about, please apply the release notes (needs details) label so that merging is blocked unless the summary release notes document is included.
• If a new flag is being introduced, review whether it is really needed. The flag names should be clear and intuitive (as far as possible), and the flag's help should be descriptive.
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Bug fixes

• There should be at least one unit or end-to-end test.
• The Pull Request description should either include a link to an issue that describes the bug OR an actual description of the bug and how to reproduce, along with a description of the fix.

Non-trivial changes

• There should be some code comments as to why things are implemented the way they are.

New/Existing features

• Should be documented, either by modifying the existing documentation or creating new documentation.
• New features should have a link to a feature request issue or an RFC that documents the use cases, corner cases and test cases.

Backward compatibility

• Protobuf changes should be wire-compatible.
• Changes to _vt tables and RPCs need to be backward compatible.
• vtctl command output order should be stable and awk-able.

[deepthi]

This needs to be forward-ported to main after merge.