Fix order of keys and values in progress meter

[devmotion]

As prior to d90910e and as done in other packages, IMO it is more natural to print "key: value" instead of "value: key".

[github-actions]

AdvancedHMC.jl documentation for PR #467 is available at:
https://TuringLang.github.io/AdvancedHMC.jl/previews/PR467/

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 75.44%. Comparing base (2f5b6c1) to head (7a2f12e).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/sampler.jl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #467   +/-   ##
=======================================
  Coverage   75.44%   75.44%           
=======================================
  Files          21       21           
  Lines        1230     1230           
=======================================
  Hits          928      928           
  Misses        302      302           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[yebai]

Thanks @devmotion!