[dashboard editor] use the theme's btn-primary

[mistercrunch]

I'm not sure why btn-primary was made black for dashboard specifically, but want to bring back consistency.

before

after

[codecov-io]

Codecov Report

Merging #6859 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #6859   +/-   ##
=======================================
  Coverage   56.31%   56.31%           
=======================================
  Files         527      527           
  Lines       23529    23529           
  Branches     2782     2782           
=======================================
  Hits        13251    13251           
  Misses       9866     9866           
  Partials      412      412

---

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[codecov-io]

Codecov Report

Merging #6859 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #6859   +/-   ##
=======================================
  Coverage   56.31%   56.31%           
=======================================
  Files         527      527           
  Lines       23529    23529           
  Branches     2782     2782           
=======================================
  Hits        13251    13251           
  Misses       9866     9866           
  Partials      412      412

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[codecov-io]

Codecov Report

Merging #6859 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #6859   +/-   ##
=======================================
  Coverage   56.31%   56.31%           
=======================================
  Files         527      527           
  Lines       23529    23529           
  Branches     2782     2782           
=======================================
  Hits        13251    13251           
  Misses       9866     9866           
  Partials      412      412

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 044f660...ec328ac. Read the comment docs.

[williaster]

@elibrumbaugh do you have thoughts on this?

[williaster]

originally this was meant to enable going to a more minimal design system, but priorities may have shifted since then. I don't have a strong opinion on it.

[mistercrunch]

I also don't have a strong opinion, I just want a single consistent btn-primary look throughout

[mistercrunch]

closes #6891

[mistercrunch]

@elibrumbaugh ping

[mistercrunch]

I'm going to merge this since it's been open for 21 days. I'm ok to revert if needed.