theme: refine height of QTabBar

src/resources/themes/v_moonlight/v_moonlight.qss

@@ -676,6 +676,7 @@ QTabBar::tab {
     border-top: $2px solid transparent;
     border-right: $1px solid @tabbar_border;
     padding: 2px 0px 2px 0px;
+    height: $20px;
 }
 
 QTabBar::tab:hover {

src/resources/themes/v_pure/v_pure.qss

@@ -676,6 +676,7 @@ QTabBar::tab {
     border-top: $2px solid transparent;
     border-right: $1px solid @tabbar_border;
     padding: 2px 0px 2px 0px;
+    height: $20px;
 }
 
 QTabBar::tab:hover {