Progress bar: content enhancements

[thyhmdo]

Discussed in https://github.com/carbon-design-system/carbon-website/discussions/3133

^{Originally posted by laurenmrice June 23, 2022}

Content enhancements

• The current progress bar component usage and style guidance has been reviewed from accessibility with requested updates.

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• Suggestions for content enhancements are provided in pdfs below:
  • Usage tab guidance: https://ibm.ent.box.com/file/953648079387?s=jvu3n241qwsynpuoit2cb6hq2byx3p7g
  • Style tab guidance: https://ibm.box.com/s/xjt4n00xi71tijvaj0fsdbiw0gtau942
  • Images with the success state need to be updated to used the $support-success color token.