fix: remove unnecessary CSS class/styling from dropdowns

[ryanahamilton]

Redo of #1491

This time leaving the filter class in place that is utilized by scripting, but still removing the undesired styling associated with it.

Description

Adhering to Bootstrap's Dropdown guidelines, the anchors within dropdown elements should not have any styled CSS classes on them. This PR removes the btn classe added in FAB as they were yielding undesirable side effects (see Airflow patch fix).

The .btn.filter styling that I removed in this PR appears to have been added by #493, but was likely only needed to begin with because of the presence of the btn class (which center aligned the text).

Before	After

ADDITIONAL INFORMATION

• Has associated issue:
• Is CRUD MVC related.
• Is Auth, RBAC security related.
• Changes the security db schema.
• Introduces new feature
• Removes existing feature

[codecov]

Codecov Report

Merging #1503 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1503   +/-   ##
=======================================
  Coverage   72.74%   72.74%           
=======================================
  Files          46       46           
  Lines        6354     6354           
=======================================
  Hits         4622     4622           
  Misses       1732     1732           

Flag	Coverage Δ
#python	72.74% <ø> (ø)

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[dpgaspar]

LGTM