Fix return type of vite command

What does this merge request do and why?

This swaps the return type of the recently introduced GDK::Services::Vite#command from array to string. This fixes a bug that keeps vite from running when calling gdk start.

Bug was first reported in slack, and I encountered it after running gdk update today.

gdk tail vite logs:

2024-10-09_20:56:37.29703 vite                  : chpst: fatal: unable to run: [support/exec-cd,: file does not exist

How to set up and validate locally

1. gdk start vite && gdk tail vite
2. logs should include something like:

2024-10-09_21:01:29.95444 vite                  : Rebuilding...
2024-10-09_21:01:34.12266 vite                  : 
2024-10-09_21:01:34.12270 vite                  : Done in 4193ms.
2024-10-09_21:01:34.12277 vite                  : Start copying files...
2024-10-09_21:01:34.52813 vite                  : Done copying 1345 files...
2024-10-09_21:01:34.56929 vite                  : 
2024-10-09_21:01:34.56931 vite                  :   VITE v5.4.8  ready in 5890 ms

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.