Remove dependency on pluralize (#1379)

## Description

[plurarize](https://www.npmjs.com/package/pluralize) is only used once
in our sdk and it brings almost no value. Also, the package itself was
last updated 6 years ago and does not support `esm`, so I think it's
better to remove this now, as it already creates problems with esm only
bundlers.

## Documentation

Does this require changes to the WorkOS Docs? E.g. the [API
Reference](https://workos.com/docs/reference) or code snippets need
updates.

```
[ ] Yes
```

If yes, link a related docs PR and add a docs maintainer as a reviewer.
Their approval is required.

Author: lucasmotta

package-lock.json

@@ -37,14 +37,12 @@
     "iron-session": "~6.3.1",
     "jose": "~5.6.3",
     "leb": "^1.0.0",
-    "pluralize": "8.0.0",
     "qs": "6.14.0"
   },
   "devDependencies": {
     "@peculiar/webcrypto": "^1.4.5",
     "@types/jest": "29.5.3",
     "@types/node": "14.18.54",
-    "@types/pluralize": "0.0.30",
     "jest": "29.6.2",
     "jest-environment-miniflare": "^2.14.2",
     "jest-fetch-mock": "^3.0.3",

package.json

@@ -1,5 +1,3 @@
-import pluralize from 'pluralize';
-
 import { UnprocessableEntityError } from '../interfaces';
 import { RequestException } from '../interfaces/request-exception.interface';
 
@@ -37,7 +35,7 @@ export class UnprocessableEntityException
     }
 
     if (errors) {
-      const requirement: string = pluralize('requirement', errors.length);
+      const requirement = errors.length === 1 ? 'requirement' : 'requirements';
 
       this.message = `The following ${requirement} must be met:\n`;