tmf.ui: set default alpha to 32 (12.5%)

The original alpha made it harder to read.

[Changed] reduced default alpha on bookmarks

Change-Id: I692d19d51bef2fa4bf41b3b763e21547b89e9444
Signed-off-by: Matthew Khouzam <matthew.khouzam@ericsson.com>

Author: MatthewKhouzam

tmf/org.eclipse.tracecompass.tmf.ui/src/org/eclipse/tracecompass/internal/tmf/ui/dialogs/AddBookmarkDialog.java

@@ -43,7 +43,7 @@ public class AddBookmarkDialog extends MultiLineInputDialog {
     private Scale fAlphaScale;
     private Label fAlphaLabel;
     private Button fForgroundButton;
-    private int fAlpha = 128;
+    private int fAlpha = 32;
     private boolean fForeground;
 
     /**