Sentence case action box message

Change-Id: I08b8af02d838c615f42974e9524978c785c9b381
diff --git a/polygerrit-ui/app/elements/diff/gr-selection-action-box/gr-selection-action-box.html b/polygerrit-ui/app/elements/diff/gr-selection-action-box/gr-selection-action-box.html
index 3993b86..5f96fce 100644
--- a/polygerrit-ui/app/elements/diff/gr-selection-action-box/gr-selection-action-box.html
+++ b/polygerrit-ui/app/elements/diff/gr-selection-action-box/gr-selection-action-box.html
@@ -32,8 +32,9 @@
         --tooltip-background-color: rgba(22, 22, 22, .9);
       }
     </style>
-    <gr-tooltip id="tooltip"
-        text="press c to comment"
+    <gr-tooltip
+        id="tooltip"
+        text="Press c to comment"
         position-below="[[positionBelow]]"></gr-tooltip>
   </template>
   <script src="gr-selection-action-box.js"></script>