chore: Use correct colour for pending workspace display (#968)

[tdmalone]

Closes #968

Description of changes:

• Sets colour for pending workspaces to the same colour used for the filter button at the top of the page (see https://github.com/awslabs/service-workbench-on-aws/blob/mainline/addons/addon-base-raas-ui/packages/base-raas-ui/src/parts/environments-sc/parts/ScEnvironmentsFilterButtons.js#L27)

Checklist:

• Have you successfully deployed to an AWS account with your changes?

• Have you successfully tested with your changes locally?

  NOTE: Testing was only done locally in the browser console, to confirm that the class applied successfully and looked as expected:
  
  

• Is this change also required on the AWS Solution version?

• If you are updating the changelog and vending out a new release, have you updated versionNumber and versionDate in .defaults.yml

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Merging #969 (db5c4c3) into develop (24010d3) will not change coverage.
The diff coverage is n/a.

❗ Current head db5c4c3 differs from pull request most recent head cfdb121. Consider uploading reports for the commit cfdb121 to get more accurate results

@@           Coverage Diff            @@
##           develop     #969   +/-   ##
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  Coverage    51.40%   51.40%           
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  Files          295      295           
  Lines        16821    16821           
  Branches      2611     2611           
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  Hits          8647     8647           
  Misses        7183     7183           
  Partials       991      991           

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[nguyen102]

I tested this and it works as expected. Thank you for your contribution!