Bug 6.8 - disabled textarea has wrong styles

[michalcharvat]

Styles

.x-form-field[readonly] {
    background-color: var(--bg-readonly);
}

are overwritten by

.x-form-duration, .x-form-text, .x-form textarea.x-form-field, .x-form-time {
    background-color: var(--bg-box);
    border: 1px solid var(--fg-track);
    display: inline-block;
    padding: 9.6px 14px;
}