[Feature] Optimize `fivetran_convert_timezone` macro

### Is there an existing feature request for this?

- [x] I have searched the existing issues

### Describe the Feature

Currently, the convert_timezone macro will only _numerically_ convert timezones and will retain a `UTC` at the end of the timestamp, regardless of the target timezone. It would be cool if we optimized this somehow -- either including the target TZ or simply remove the UTC.

I'm not actually sure how feasible this is or if it would cause more trouble than it's worth, but throwing it out there!

### How would you implement this feature?

Either cut off the UTC or replace it with the actual target TZ.

### Describe alternatives you've considered

leave as is

### Are you interested in contributing this feature?

- [ ] Yes.
- [ ] Yes, but I will need assistance.
- [ ] No.

### Anything else?

_No response_