Fix some preferences layout issues

- Replace -moz-box- properties with flex equivalents
- Remove some of the old useless CSS
- Replace non-RTL-aware text-aligns

scss/preferences.scss

@@ -40,7 +40,7 @@
 	flex-direction: row;
 	min-width: 0;
 	min-height: 0;
-	-moz-box-flex: 1;
+	flex: 1;
 	background-color: var(--material-sidepane);
 	// See scss/win/abstracts/mixin
 	--color-form-element-base-background: var(--material-sidepane);
@@ -83,7 +83,6 @@
 
 #prefs-search {
 	width: 16em;
-	-moz-box-pack: end;
 }
 
 #prefs-navigation {
@@ -97,7 +96,7 @@
 	& > richlistitem {
 		padding: 1em;
 		border-radius: 5px;
-		-moz-box-align: center;
+		align-items: center;
 		font-size: 1.1em;
 		transition: background-color 0.2s ease;
 		-moz-context-properties: fill, fill-opacity;
@@ -228,11 +227,6 @@ groupbox:not(:first-of-type) label > h2 {
 	display: none !important;
 }
 
-prefwindow .chromeclass-toolbar
-{
-	display: -moz-box !important; /* Ignore toolbar collapse button on OS X */
-}
-
 window[windowtype="zotero:pref"] {
    min-width: 600px;
 }
@@ -247,14 +241,6 @@ description, label, checkbox {
 	max-width: 630px;
 }
 
-radio[pane]
-{
-	min-width: 5.5em;
-	height: 48px;
-	-moz-box-align: center;
-	-moz-box-pack: end;
-}
-
 checkbox[disabled="true"] {
 	color: gray !important;
 }
@@ -289,7 +275,7 @@ description label[class=zotero-text-link], label[class=zotero-text-link]
 	row-gap: .3em;
 
 	& > :nth-child(odd) {
-		-moz-box-pack: end; /* Right-justify left column */
+		justify-self: end; /* Right-justify left column */
 	}
 }
 

scss/preferences/_advanced.scss

@@ -31,7 +31,7 @@
 
 #zotero-prefpane-advanced-feeds-feedDefaults .html-input {
 	width: 50px;
-	text-align: right;
+	text-align: end;
 }
 
 #zotero-prefpane-advanced-feeds-feedDefaults hbox {
@@ -52,7 +52,7 @@
 
 #zotero-prefpane-advanced-open-buttons {
 	display: block;
-	text-align: right;
+	text-align: end;
 	margin-top: 1em;
 	margin-bottom: .5em;
 }
@@ -67,5 +67,5 @@
 
 #fulltext-stats > .form-grid > label:nth-child(odd)
 {
-	text-align: right;
+	text-align: end;
 }

scss/preferences/_export.scss

@@ -18,6 +18,6 @@
 
 #noteQuickCopy-format-options th {
 	font-weight: normal;
-	text-align: right;
+	text-align: end;
 	max-width: 3.6em;
 }

scss/preferences/_sync.scss

@@ -4,12 +4,12 @@
 }
 
 #zotero-prefpane-sync .form-grid > hbox {
-	-moz-box-align: center;
+	align-items: center;
 }
 
 #zotero-prefpane-sync .form-grid > label:nth-child(odd)
 {
-	text-align: right;
+	text-align: end;
 }
 
 #zotero-prefpane-sync .form-grid > hbox