plugin-redirects: small improvement on deepMerge

[donwellus]

Description

It is a very small change that is not intended to change behavior of the function deepMerge.

• I have read and understand the CONTRIBUTING.md document in this repository.

Type of change

• Chore (non-breaking change which does not add functionality)

Checklist:

• Existing test suite passes locally with my changes

$ pnpm test:int plugin-redirects

> payload-monorepo@0.0.1 test:int /home/.../payload
> cross-env DISABLE_LOGGING=true jest --forceExit --detectOpenHandles "plugin-redirects"

Determining test suites to run...

No database specified, using default
 PASS  test/plugin-redirects/int.spec.ts (12.895 s)
  Redirects Plugin
    ✓ should add a redirects collection (10 ms)
    ✓ should add a redirect with to internal page (14 ms)
    ✓ should add a redirect with to custom url (9 ms)

Test Suites: 1 passed, 1 total
Tests:       3 passed, 3 total
Snapshots:   0 total
Time:        12.925 s
Ran all test suites matching /plugin-redirects/i.

Hi there o/

This is my first PR here, I hope I did everything according to the guidelines in the project documentation. If not, let me know and I'll adjust as necessary.

Have a nice week =)