Fix prefs window style on MacOS (#4682)

Use MacOS menupopup style to prefs window
Move style mac/menupopup into mac/components

chrome/content/zotero-platform/mac/preferences.css

@@ -1,26 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-window[windowtype="zotero:pref"] {
-	padding: 0;
-	font: -moz-dialog !important;
-	
-	-moz-appearance: dialog;
-	color: -moz-DialogText;
-}
-
-groupbox > label > h2, groupbox > * > label > h2 {
-	border-bottom: #b5b5b5 1px solid;
-}
-
-groupbox > label > h2, groupbox > * > label > h2, caption {
-	padding-bottom: 0.2em;
-	font: caption;
-}
-
-.help-button {
-	appearance: auto;
-	-moz-default-appearance: -moz-mac-help-button;
-	min-width: 0;
-}

scss/mac/_helpButton.scss

@@ -0,0 +1,5 @@
+.help-button {
+	appearance: auto;
+	-moz-default-appearance: -moz-mac-help-button;
+	min-width: 0;
+}

scss/preferences-mac.scss

@@ -0,0 +1,19 @@
+// Abstracts
+
+@import "abstracts/variables";
+@import "abstracts/functions";
+@import "abstracts/mixins";
+@import "abstracts/placeholders";
+@import "abstracts/utilities";
+@import "abstracts/split-button";
+@import "abstracts/svgicon";
+
+@import "themes/light";
+@import "themes/dark";
+
+@import "mac/helpButton";
+
+// Components
+
+@import "mac/components/menupopup";
+@import "mac/components/menulist";

scss/zotero-mac.scss

@@ -9,7 +9,7 @@
 @import "mac/tabBar";
 @import "mac/tabbox";
 @import "mac/titleBar";
-@import "mac/menupopup";
+@import "mac/components/menupopup";
 @import "mac/components/menulist";
 
 // Elements