`patch-package --partial` returns errors for incorrect patch

First of all, thanks again for all of the hard work and maintenance that goes into `patch-package`. It's also an inspiration for other tools in the ecosystem, leading to the `pnpm patch` feature (although `patch-package` is still a bit ahead in terms of DX).

I noticed a new error message which I thought showed an exciting [new feature called `--partial`](https://github.com/ds300/patch-package#partially-applying-a-broken-patch-file):

```bash
⛔ ERROR

Failed to apply patch file next+13.4.18.patch.

If this patch file is no longer useful, delete it and run

patch-package

To partially apply the patch (if possible) and output a log of errors to fix, run

patch-package --partial

After which you should make any required changes inside node_modules/next, and finally run

patch-package next

to update the patch file.
```

So I decided to give it a try, and ran `yarn patch-package --partial`:

```bash
$ yarn patch-package --partial
patch-package 8.0.0
Applying patches...
Saving errors to ./patch-package-errors.log
```

...as expected, I received errors - I expected these errors to match the updated `next` package and the patch which was failing, so that I could manually edit the offending files in `node_modules/next`.

However, the error log file contained errors about a completely different patch - one that actually does not have troubles applying, if I revert the version of the offending `next` package.

`./patch-package-errors.log`

````
Cannot apply hunk 0 for file node_modules/check-links/lib/check-link.js
```diff
@@ -3,6 +3,7 @@
const got = require('got')
const isRelativeUrl = require('is-relative-url')
const parse = require('url').parse
+const userAgents = require('top-user-agents')

const protocolWhitelist = new Set([
'https:',
```

Cannot apply hunk 1 for file node_modules/check-links/lib/check-link.js
```diff
@@ -3,6 +3,7 @@
const got = require('got')
const isRelativeUrl = require('is-relative-url')
const parse = require('url').parse
+const userAgents = require('top-user-agents')

const protocolWhitelist = new Set([
'https:',
@@ -89,4 +90,4 @@ module.exports.isValidUrl = (url, opts) => {
}
}

-module.exports.userAgent = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36'
+module.exports.userAgent = userAgents[Math.floor(Math.random() * (userAgents.length - 1))]
```
````

---

One potentially related thing is that I noticed that `patch-package` started [retaining old, obsolete patch files](https://github.com/ds300/patch-package/issues/480) when upgrading dependencies, and this was also the case for the `next` package - I had two identical patches from when I ran `yarn patch-package next` the last time I upgraded versions. However, this does not appear to be related to `--partial` mode, because:

1. Removing the extra patch file did not resolve the bug reported above
2. The extra patch file was not causing any other problems