MM-61526 Fix scrollbar not clickable due to being covered by toaster (#29251)

* Fix scrollbar not clickable due to being covered by toaster

* Apply suggestions from code review

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Co-authored-by: Harrison Healey <harrisonmhealey@gmail.com>
Co-authored-by: Mattermost Build <build@mattermost.com>

webapp/channels/src/components/toast_wrapper/toast__wrapper.scss

@@ -2,9 +2,9 @@
     position: absolute;
     z-index: 3;
     display: flex;
-    width: 100%;
+    width: calc(100% - 32px);
     align-items: center;
     justify-content: center;
-    margin-top: 16px;
+    margin: 16px 16px 0;
     gap: 7px;
 }