chore: remove src/client from package

[sapphi-red]

Description

These 12e0550, 294d8b4 commits added src/client to files field of package.json to include them in the package to avoid sourcemap errors.
But now dist/client/client.mjs.map has sourcesContent field so the real files in src/client is not needed.

I tested #3652's reproduction by upgrading Vite to 2.9.15 and manually removing src/client from the vite package.

Additional context

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the Commit Convention.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

[silverwind]

The source map files in latest release still point to the removed files which causes warnings during dev for me:

Sourcemap for "node_modules/vite/dist/client/client.mjs" points to missing source files
Sourcemap for "node_modules/vite/dist/client/env.mjs" points to missing source files

Inspecting one of the sourcemap files shows the reference to nonexistant files:

{"version":3,"file":"client.mjs","sources":["../../src/client/overlay.ts","../../src/client/client.ts"]}

These warnings do not seem to reproduce using default config at least.

[patak-dev]

@silverwind would you create a minimal reproduction to send a new issue so we can properly track this?

[silverwind]

Yes, if I find the config option that causes it.

[alamhubb]

最新版本中的源映射文件仍然指向已删除的文件，这会在我的开发过程中引起警告：

Sourcemap for "node_modules/vite/dist/client/client.mjs" points to missing source files
Sourcemap for "node_modules/vite/dist/client/env.mjs" points to missing source files

检查其中一个源映射文件会显示对不存在文件的引用：

{"version":3,"file":"client.mjs","sources":["../../src/client/overlay.ts","../../src/client/client.ts"]}

至少使用默认配置似乎不会重现这些警告。

+1，I also encountered this problem ，

[adminoid]

+1 same issue... :-(

[patak-dev]

Please create new issues with a minimal reproduction, dont comment on old PRs