Make Add Indexer modal height fixed

frontend/src/Settings/Indexers/Indexers/AddIndexerModal.css

@@ -0,0 +1,5 @@
+.modal {
+  composes: modalBody from '~Components/Modal/Modal.css';
+
+  height: 90%;
+}

frontend/src/Settings/Indexers/Indexers/AddIndexerModal.js

@@ -2,12 +2,14 @@ import PropTypes from 'prop-types';
 import React from 'react';
 import Modal from 'Components/Modal/Modal';
 import AddIndexerModalContentConnector from './AddIndexerModalContentConnector';
+import styles from './AddIndexerModal.css';
 
 function AddIndexerModal({ isOpen, onModalClose, ...otherProps }) {
   return (
     <Modal
       isOpen={isOpen}
       onModalClose={onModalClose}
+      className={styles.modal}
     >
       <AddIndexerModalContentConnector
         {...otherProps}