Fix theming of Save Connection button (fixes #798)

[gjsjohnmurray]

This PR fixes #798

With Monokai theme now:

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• [x] Your code builds clean without any errors or warnings
• [x] You have made the needed changes to the docs
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[codecov[bot]]

Codecov Report

Merging #965 (1701682) into dev (37c6ad0) will not change coverage. The diff coverage is 0.00%.

@@           Coverage Diff           @@
##              dev     #965   +/-   ##
=======================================
  Coverage   10.00%   10.00%           
=======================================
  Files         175      175           
  Lines        5867     5867           
  Branches     1376     1376           
=======================================
  Hits          587      587           
  Misses       5280     5280           

Flag	Coverage Δ
extension	10.00% <0.00%> (ø)
formatter	100.00% <ø> (ø)

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

Impacted Files	Coverage Δ
...ttings/components/SettingsFormStepWidget/index.tsx	0.00% <0.00%> (ø)

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[mtxr]

LGTM. I've tested with some themes, both dark and light. all looking good.