AppCenter language translation branding

### Problem

In at least some languages (and Spanish and French for certain), AppCenter is translated in elementary as the generic "center for applications". That is, AppCenter shows up in elementary as "Centre d’Applications" in French and "Centro de aplicaciones" in Spanish.

For consistent branding and brand building, the team should consider using the branded name "AppCenter" across languages. For point of reference, Apple uses "el App Store" and Google uses "el Google Play Store" when referencing their app stores Spanish.

### Proposal

Make a decision about whether AppCenter should be titled "AppCenter" in translated languages, and if so, make translations consistent. This decision could apply to other elementary apps as well, but for AppCenter it seemed especially important, and more so now that AppCenter is being used in other distributions too.

### Prior Art (Optional)

_No response_