Remove icon since MailPoet's modal has no such thing

[MAILPOET-2804]

assets/css/src/components-plugin/_modal.scss

@@ -112,16 +112,6 @@
   justify-content: left;
 }
 
-.mailpoet-modal-header-icon-container {
-  display: inline-block;
-
-  svg {
-    max-height: $modal-icon-button-size;
-    max-width: $modal-icon-button-size;
-    padding: $modal-grid-size;
-  }
-}
-
 // Modal contents.
 .mailpoet-modal-content {
   box-sizing: border-box;

assets/css/src/settings/_modal.scss

@@ -2,7 +2,6 @@ $modal-border-width: 1px;
 $modal-dark-gray-900: #191e23;
 $modal-header-height: 56px;
 $modal-header-z-index: 10;
-$modal-icon-button-size: 36px;
 $modal-light-gray-500: #e2e4e7;
 $modal-min-width: 360px;
 $modal-screen-overlay-z-index: 100000;

assets/js/src/common/modal/header.jsx

@@ -5,7 +5,6 @@ import { Button } from '@wordpress/components';
 import closeIcon from './close_icon.jsx';
 
 const ModalHeader = ({
-  icon,
   title,
   onClose,
   headingId,
@@ -13,14 +12,6 @@ const ModalHeader = ({
 }) => (
   <div className="mailpoet-modal-header">
     <div className="mailpoet-modal-header-heading-container">
-      { icon && (
-        <span
-          className="mailpoet-modal-icon-container"
-          aria-hidden
-        >
-          { icon }
-        </span>
-      ) }
       { title && (
         <h1
           id={headingId}
@@ -40,7 +31,6 @@ ModalHeader.propTypes = {
   title: PropTypes.string,
   headingId: PropTypes.string,
   onClose: PropTypes.func,
-  icon: PropTypes.node,
   isDismissible: PropTypes.bool,
 };
 
@@ -48,7 +38,6 @@ ModalHeader.defaultProps = {
   title: null,
   headingId: 'heading-id',
   onClose: () => {},
-  icon: null,
   isDismissible: true,
 };
 

assets/js/src/common/modal/modal.jsx

@@ -8,7 +8,6 @@ import ModalHeader from './header.jsx';
 function Modal({
   onRequestClose,
   title,
-  icon,
   displayTitle,
   children,
   aria,
@@ -46,7 +45,6 @@ function Modal({
           displayTitle && (
             <ModalHeader
               headingId={headingId}
-              icon={icon}
               isDismissible={isDismissible}
               onClose={onRequestClose}
               title={title}
@@ -78,7 +76,6 @@ Modal.propTypes = {
   shouldCloseOnEsc: PropTypes.bool,
   shouldCloseOnClickOutside: PropTypes.bool,
   role: PropTypes.string,
-  icon: PropTypes.node,
 };
 
 Modal.defaultProps = {
@@ -86,7 +83,6 @@ Modal.defaultProps = {
   onRequestClose: () => {},
   role: 'dialog',
   title: null,
-  icon: null,
   aria: {},
   focusOnMount: true,
   shouldCloseOnEsc: true,