Update IconButton colors (#30124)

* chore: update `@vector-im/compound-web` to 8.0.0

* refactor(IconButton): use `kind="secondary"` instead of `subtleBackground` props

* test: update snapshots

* fix: force color on room header toggle

* fix: TAC button color

* test(e2e): update release announcement screenshot

test/unit-tests/components/views/settings/tabs/user/__snapshots__/EncryptionUserSettingsTab-test.tsx.snap

@@ -178,7 +178,8 @@ exports[`<EncryptionUserSettingsTab /> should display the reset identity panel w
       >
         <button
           aria-label="Back"
-          class="_icon-button_m2erp_8 _subtle-bg_m2erp_29"
+          class="_icon-button_1pz9o_8"
+          data-kind="secondary"
           role="button"
           style="--cpd-icon-button-size: 28px;"
           tabindex="0"