UI: Fix scene/source list item spacing

UI/data/themes/Acri.qss

@@ -142,7 +142,6 @@ SourceTree::item {
 	margin-bottom: 2px;
 	margin-top: 0px;
 	border: 1px solid transparent;
-	height: 24px;
 }
 
 QListWidget QLineEdit {

UI/data/themes/Dark.qss

@@ -701,11 +701,6 @@ OBSBasicSettings QListWidget::item {
     padding-bottom: 5px;
 }
 
-QListWidget::item,
-SourceTree::item {
-	height: 24px;
-}
-
 /* Locked CheckBox */
 
 LockedCheckBox {

UI/data/themes/Rachni.qss

@@ -184,11 +184,6 @@ QListWidget::item:hover:!active {
 	border: none;
 }
 
-QListWidget::item,
-SourceTree::item {
-	height: 24px;
-}
-
 /***********************/
 /* --- Dock widget --- */
 /***********************/

UI/data/themes/System.qss

@@ -229,11 +229,6 @@ OBSBasic {
     qproperty-defaultIcon: url(:res/images/sources/default.svg);
 }
 
-QListWidget::item,
-SourceTree::item {
-	height: 24px;
-}
-
 /* Scene Tree */
 
 SceneTree {