[CR-2057]: Remove email placeholder (#23739)

* Remove email placeholder

The current placeholder is confusing to users and results in many trying
to login with their username. The change in this PR hopefully decreases that
confusion.

According to UX recommendations, we have decided to remove the email placeholder for the form. It seems placeholders tend to just confuse the users.

openedx/core/djangoapps/user_authn/views/login_form.py

@@ -89,15 +89,11 @@ def get_login_session_form(request):
 
     # Translators: This label appears above a field on the login form
     # meant to hold the user's email address.
-    email_label = _(u"Email")
-
-    # Translators: This example email address is used as a placeholder in
-    # a field on the login form meant to hold the user's email address.
-    email_placeholder = _(u"username@domain.com")
+    email_label = _("Email")
 
     # Translators: These instructions appear on the login form, immediately
     # below a field meant to hold the user's email address.
-    email_instructions = _(u"The email address you used to register with {platform_name}").format(
+    email_instructions = _("The email address you used to register with {platform_name}").format(
         platform_name=configuration_helpers.get_value('PLATFORM_NAME', settings.PLATFORM_NAME)
     )
 
@@ -105,7 +101,6 @@ def get_login_session_form(request):
         "email",
         field_type="email",
         label=email_label,
-        placeholder=email_placeholder,
         instructions=email_instructions,
         restrictions={
             "min_length": accounts.EMAIL_MIN_LENGTH,

openedx/core/djangoapps/user_authn/views/tests/test_login.py

@@ -811,8 +811,8 @@ class LoginSessionViewTest(ApiTestCase):
                 "type": "email",
                 "required": True,
                 "label": "Email",
-                "placeholder": "username@domain.com",
-                "instructions": u"The email address you used to register with {platform_name}".format(
+                "placeholder": "",
+                "instructions": "The email address you used to register with {platform_name}".format(
                     platform_name=settings.PLATFORM_NAME
                 ),
                 "restrictions": {