chore: Translate pressbooks-aldine.pot in es

72% of minimum 25% translated source file: 'pressbooks-aldine.pot'
on 'es'.

Sync of partially translated files: 
untranslated content is included with an empty translation 
or source language content depending on file format

languages/pressbooks-aldine-es_ES.po

@@ -520,11 +520,11 @@ msgstr "El nombre es obligatorio."
 
 #: inc/helpers/namespace.php:479
 msgid "Email is required."
-msgstr ""
+msgstr "El correo electrónico es obligatorio."
 
 #: inc/helpers/namespace.php:483
 msgid "Email is invalid."
-msgstr ""
+msgstr "El correo electrónico no es valido."
 
 #: inc/helpers/namespace.php:487
 msgid "Institution is required."