UI: Update 'ready' chip's style to 'success'

The task tree view has a green icon for ready tasks. Change the chip's
style as well to be consistent.

Change-Id: I6fa2d7be096ca2c09e0d1999bd52126a43ae39bf

gr-task-plugin/gr-task-chip_html.js

diff --git a/gr-task-plugin/gr-task-chip_html.js b/gr-task-plugin/gr-task-chip_html.js
index 68e1d0c..f319248 100644
--- a/gr-task-plugin/gr-task-chip_html.js
+++ b/gr-task-plugin/gr-task-chip_html.js
@@ -58,15 +58,15 @@
       background: var(--warning-background-focus);
     }
     .taskSummaryChip.ready {
-      border-color: var(--warning-foreground);
-      background: var(--warning-background);
+      border-color: var(--success-foreground);
+      background: var(--success-background);
     }
     .taskSummaryChip.ready:hover {
-      background: var(--warning-background-hover);
+      background: var(--success-background-hover);
       box-shadow: var(--elevation-level-1);
     }
     .taskSummaryChip.ready:focus-within {
-      background: var(--warning-background-focus);
+      background: var(--success-background-focus);
     }
     .taskSummaryChip.invalid {
       color: var(--error-foreground);