remove zlib in favour of built in

Creating new prototypes is (silently) failing when using npm v10.4.0 or newer because of an error that occurs when installing the `zlib` package:

```
$ npm install zlib
npm ERR! code 127
npm ERR! path /Users/oliver.byford/Code/zlib-test/node_modules/zlib
npm ERR! command failed
npm ERR! command sh -c node-waf clean || true; node-waf configure build
npm ERR! sh: node-waf: command not found
npm ERR! sh: node-waf: command not found
```

The `zlib` package is 13 years old, and has been replaced by a zlib ‘core module’ built into node itself since Node v0.6.

`require(‘zlib’)` will always return the core module [1] over a dependency from `node_modules`, and so despite being listed as a dependency the `zlib` package will never be used [2] and can safely be removed.

[1]: https://nodejs.org/api/modules.html#modules_all_together
[2]: kkaefer/DEPRECATED-node-zlib#7

Co-authored-by: Oliver Byford <oliver.byford@digital.cabinet-office.gov.uk>

package.json

@@ -84,8 +84,7 @@
     "sync-request": "^6.1.0",
     "tar-stream": "^3.1.7",
     "universal-analytics": "^0.5.3",
-    "uuid": "^9.0.1",
-    "zlib": "^1.0.5"
+    "uuid": "^9.0.1"
   },
   "devDependencies": {
     "cheerio": "^1.0.0-rc.12",