fix: remove unnecessary CSS classes from dropdowns

[ryanahamilton]

Description

Adhering to Bootstrap's Dropdown guidelines, the anchors within dropdown elements should not have any CSS classes on them. This PR removes classes 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 #1491 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1491   +/-   ##
=======================================
  Coverage   72.73%   72.73%           
=======================================
  Files          46       46           
  Lines        6352     6352           
=======================================
  Hits         4620     4620           
  Misses       1732     1732           

Flag	Coverage Δ
#python	72.73% <ø> (ø)

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