fix: fix CreateExperiment for Remote Users

[salonig23]

Description

taskSpec.ExtraEnvVars was not initialized in the case of remote users which was causing a panic whenever the user tried to create an experiment

Test Plan

Log in as a remote user and check if you can create an experiment

Commentary (optional)

Checklist

• Changes have been manually QA'd
• User-facing API changes need the "User-facing API Change" label.
• Release notes should be added as a separate file under docs/release-notes/.
  See Release Note for details.
• Licenses should be included for new code which was copied and/or modified from any external code.

Ticket

[netlify]

✅ Deploy Preview for determined-ui canceled.

Name	Link
🔨 Latest commit	fcb69e2
🔍 Latest deploy log	https://app.netlify.com/sites/determined-ui/deploys/65a811547332150008b4c358

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (6ccc7dc) 48.95% compared to head (fcb69e2) 45.58%.
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8700      +/-   ##
==========================================
- Coverage   48.95%   45.58%   -3.38%     
==========================================
  Files         634      701      +67     
  Lines       81788   142197   +60409     
  Branches        0     2088    +2088     
==========================================
+ Hits        40042    64817   +24775     
- Misses      40261    75887   +35626     
- Partials     1485     1493       +8     

Flag	Coverage Δ
harness	37.21% <ø> (-26.05%)	⬇️
web	53.77% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
master/internal/api_experiment.go	45.42% <100.00%> (+0.06%)	⬆️
master/internal/experiment.go	21.19% <0.00%> (+0.03%)	⬆️

... and 527 files with indirect coverage changes