perf: trim keys once

[VIKTORVAV99]

Trims the key once and reuse it rather than calling trim multiple times. Also moves the logic inside the if condition instead of using an early return since it's the only logic in there.

This should improve both the performance and bundle size a tiny bit.

Checklist

• only relevant code is changed (make a diff before you submit the PR)
• run tests npm run test
• tests are included
• commit message and code follows the Developer's Certification of Origin

Checklist (for documentation change)

• only relevant documentation part is changed (make a diff before you submit the PR)
• motivation/reason is provided
• commit message and code follows the Developer's Certification of Origin

[coveralls]

coverage: 96.317% (+0.004%) from 96.313%
when pulling bea33b4 on VIKTORVAV99:trim_keys_once
into 20011af on i18next:master.

[adrai]

included in v23.11.5