Decrease size of Clear All History icon

Previously was set at the default size of 24px, this change
reduces its size to 20px.

Bug: 1106551
Change-Id: I34f2faff0799b6125c05a683d9619b2c59579534
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2303231Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Jimmy Gong <jimmyxgong@chromium.org>
Cr-Commit-Position: refs/heads/master@{#789312}

chromeos/components/print_management/resources/print_management.html

@@ -31,6 +31,8 @@
   }
 
   #deleteIcon {
+    --iron-icon-height: 20px;
+    --iron-icon-width: 20px;
     margin-inline-end: 4px;
   }