chore: remove unused files from published package

Prevents the following being included in the npm tarball:

- `src`: we may want to ship this if we shipped source maps, so
  users could click on internal lines in stack traces, but we don't
  ship source maps to npm, so these aren't needed.
- `miniflare-config-stubs`: these aren't used as of #633
  (https://github.com/cloudflare/workers-sdk/pull/633/files#diff-dd2c9d6fc577a3da1b7cf0b6b4a0705a1c71eb5d99c372d5bdda99476362f975L97-L102)
- `vendor`: this directory doesn't actually exist in the `wrangler`
   package directory, there is a root `vendor` directory, but files
   from that are copied to `wrangler-dist` during build

Closes #3013

.changeset/spotty-apricots-eat.md

@@ -0,0 +1,7 @@
+---
+"wrangler": major
+---
+
+chore: remove unused files from published package
+
+Specifically, the `src` and `miniflare-config-stubs` directories have been removed.

packages/wrangler/package.json

@@ -42,14 +42,10 @@
 		"wrangler2": "./bin/wrangler.js"
 	},
 	"files": [
-		"src",
 		"bin",
-		"miniflare-config-stubs",
 		"miniflare-dist",
 		"wrangler-dist",
 		"templates",
-		"vendor",
-		"import_meta_url.js",
 		"kv-asset-handler.js",
 		"Cloudflare_CA.pem"
 	],