MM-53814 - Updating contrast for accessibility (#24381)

* Updating contrast for accessiblity

* Updating accessbility

* Updating accessiblity for icons

* Updating header icons

* Updating text opacity

* Updating icons and text

* Updating sidebar left

* Upadating icon in system console

* Updating global header

* Updating channel list

* Updating tests and fixing conflicts

* Updating filter css

* Updating css

* Updating epehemeral message contrast

* Updating icon with 64 opacity

* Updating test

* Updating confirm license removal csss

* Updating unintended files

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Co-authored-by: Mattermost Build <build@mattermost.com>

webapp/channels/src/plugins/call_button/call_button.scss

@@ -43,7 +43,7 @@ button {
         }
 
         &.dropdown {
-            color: rgba(var(--center-channel-color-rgb), 0.56);
+            color: rgba(var(--center-channel-color-rgb), 0.75);
             fill: currentColor;
         }
 
@@ -94,7 +94,7 @@ button {
 
             .call-button-dropdown-sublabel {
                 margin-top: 4px;
-                color: rgba(var(--center-channel-color-rgb), 0.56);
+                color: rgba(var(--center-channel-color-rgb), 0.75);
                 font-size: 12px;
                 line-height: 16px;
             }