More Label touchups (margins) (#10722)

* labels with onClick don't need .pointer. No labels need `m-r-5`

* making Timer a proper Label

* a little linting

* addresing (helpful, thanks) comment

superset-frontend/src/explore/components/ExploreChartHeader.jsx

@@ -72,8 +72,9 @@ const StyledHeader = styled.div`
     align-items: center;
     justify-content: flex-end;
 
-    .btn-group {
+    > .btn-group {
       flex: 0 0 auto;
+      margin-left: ${({ theme }) => theme.gridUnit}px;
     }
   }
 `;