Aligns Commit Graph header column icons

src/webviews/apps/plus/graph/graph.scss

@@ -862,7 +862,7 @@ button:not([disabled]),
 
 	.graph-icon {
 		position: relative;
-		top: -3px;
+		top: -2px;
 		color: var(--text-disabled, hsla(0, 0%, 100%, 0.4));
 	}
 }