Revert "Fix: Theme milestone progress bar statuses not rendered correctly"

This reverts commit a705ab8ab4.

public/assets/css/theme-bthree-dark.css

@@ -518,24 +518,6 @@ a.ui.primary.label:hover,
 	 color: #dbdbeb;
 }
 
-/* Progress bar. */
-progress {
-  appearance: none; /* Remove default styling */
-  background-color: var(--color-secondary); /* Fallback colour bg (unfilled portion) */
-  border: none; /* remove default border */
-
-  -moz-appearance: none;
-  -webkit-appearance: none;
-}
-
-progress::-webkit-progress-value {
-  background-color: var(--color-primary); /* Color of the filled portion */
-}
-
-progress::-moz-progress-bar {
-  background-color: var(--color-primary); /* Color of the filled portion */
-}
-
 /* Style Overrides. */
 #navbar .dropdown .item {
   justify-content: flex-start !important;