build: fix npm package files inclusion

We are publishing with yarn 1, which has a problem with negation
patterns in "files" list, causing the npm package to include every
file in the directory.

Since the original reason to expose src files was to address #3652,
which is a client-only concern, we can include the `/client` dir only.
This avoids having to exclude tests in `/node` and also reduces
package size.

packages/vite/package.json

@@ -13,9 +13,8 @@
     "bin",
     "dist",
     "client.d.ts",
-    "src",
-    "types",
-    "!/src/**/__tests__/"
+    "src/client",
+    "types"
   ],
   "engines": {
     "node": ">=12.2.0"