fix: light theme desktop app top white notch situation

Author: abose

src/styles/brackets.less

@@ -289,6 +289,10 @@ a, img {
     border-bottom: 1px solid @bc-panel-border;
     box-shadow: 0 1px 3px @bc-shadow-small;
     font-size: @menu-item-font-size;
+    border-top: 1px solid @border-title-bar;
+    .dark & {
+        border-top: none;
+    }
 
     // Make sure the bottom box-shadow goes above the editor (position: relative needed to start a new stacking group)
     position: relative;

src/styles/brackets_core_ui_variables.less

@@ -51,6 +51,7 @@
 @bc-bg-highlight:               #e0f0fa;
 @bc-bg-inline-widget:           #e6e9e9;
 @bc-bg-tool-bar:                #5D5F60;
+@border-title-bar:              #d5d5d5;
 @bc-bg-status-bar:              #fff;
 @bc-bg-status-bar-height:       26px;
 @bc-disabled-opacity:           0.3;