tweak service icon shadow

src/scss/_dashboard.scss

@@ -471,7 +471,7 @@
 }
 
 .UppyDashboardItem-sourceIcon .UppyIcon {
-  filter: drop-shadow(0 0 1px rgba(0,0,0,.15));
+  filter: drop-shadow(0 0 1px rgba(0,0,0,0.3));
 }
 
 .UppyDashboardItem-previewInnerWrap {