Remove displayTitle prop, use title only

[MAILPOET-2777]

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

@@ -10,11 +10,9 @@ const ModalHeader = ({
 }) => (
   <div className="mailpoet-modal-header">
     <div className="mailpoet-modal-header-heading-container">
-      { title && (
       <h1 className="mailpoet-modal-header-heading">
         { title }
       </h1>
-      ) }
     </div>
     { isDismissible && (
       <button type="button" onClick={onClose} className="mailpoet-modal-close">{closeIcon}</button>
@@ -23,13 +21,12 @@ const ModalHeader = ({
 );
 
 ModalHeader.propTypes = {
-  title: PropTypes.string,
+  title: PropTypes.string.isRequired,
   onClose: PropTypes.func,
   isDismissible: PropTypes.bool,
 };
 
 ModalHeader.defaultProps = {
-  title: null,
   onClose: () => {},
   isDismissible: true,
 };

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

@@ -8,7 +8,6 @@ import ModalHeader from './header.jsx';
 function Modal({
   onRequestClose,
   title,
-  displayTitle,
   children,
   isDismissible,
   shouldCloseOnEsc,
@@ -32,15 +31,13 @@ function Modal({
         className="mailpoet-modal-content"
         role="document"
       >
-        {
+        { title && (
-          displayTitle && (
           <ModalHeader
             isDismissible={isDismissible}
             onClose={onRequestClose}
             title={title}
           />
-          )
+        ) }
-        }
         { children }
       </div>
     </ModalFrame>,
@@ -55,7 +52,6 @@ Modal.propTypes = {
   overlayClassName: PropTypes.string,
   title: PropTypes.string,
   onRequestClose: PropTypes.func,
-  displayTitle: PropTypes.bool,
   fullScreen: PropTypes.bool,
   focusOnMount: PropTypes.bool,
   shouldCloseOnEsc: PropTypes.bool,
@@ -72,7 +68,6 @@ Modal.defaultProps = {
   shouldCloseOnEsc: true,
   shouldCloseOnClickOutside: true,
   isDismissible: true,
-  displayTitle: true,
   fullScreen: false,
 };