chore: title bar border coro in light theme

Author: abose

src/styles/brackets_core_ui_variables.less

@@ -51,7 +51,7 @@
 @bc-bg-highlight:               #e0f0fa;
 @bc-bg-inline-widget:           #e6e9e9;
 @bc-bg-tool-bar:                #5D5F60;
-@border-title-bar:              #d5d5d5;
+@border-title-bar:              #e7e7e7;
 @bc-bg-status-bar:              #fff;
 @bc-bg-status-bar-height:       26px;
 @bc-disabled-opacity:           0.3;