Fix back button on sign-up pages (#5376)

webapp/components/signup/components/signup_email.jsx

@@ -459,7 +459,7 @@ export default class SignupEmail extends React.Component {
         return (
             <div>
                 <div className='signup-header'>
-                    <Link to='/signup_user_complete'>
+                    <Link to='/'>
                         <span className='fa fa-chevron-left'/>
                         <FormattedMessage
                             id='web.header.back'

webapp/components/signup/components/signup_ldap.jsx

@@ -215,7 +215,7 @@ export default class SignupLdap extends React.Component {
         return (
             <div>
                 <div className='signup-header'>
-                    <Link to='/signup_user_complete'>
+                    <Link to='/'>
                         <span className='fa fa-chevron-left'/>
                         <FormattedMessage
                             id='web.header.back'