Update note actions icon color

Use gray-600 for color
Ensure passes accessibility reqs

app/assets/stylesheets/framework/mixins.scss

@@ -325,8 +325,8 @@
   line-height: 1;
   padding: 0;
   min-width: 16px;
-  color: $gray-darkest;
-  fill: $gray-darkest;
+  color: $gray-600;
+  fill: $gray-600;
 
   .fa {
     position: relative;

app/assets/stylesheets/pages/notes.scss

@@ -645,7 +645,7 @@ $note-form-margin-left: 72px;
   display: inline-flex;
   align-items: center;
   margin-left: 10px;
-  color: $gray-darkest;
+  color: $gray-600;
 
   @include notes-media('max', map-get($grid-breakpoints, sm) - 1) {
     float: none;

changelogs/unreleased/62061-note-icon-color.yml

+---
+title: Update icon color to match design system, pass accessibility
+merge_request: 28498
+author: Jarek Ostrowski @jareko
+type: fixed