fix: clarify "Replace" in I-D submission form

ietf/submit/forms.py

@@ -502,7 +502,7 @@ def clean_name(self):
         return name
 
 class ReplacesForm(forms.Form):
-    replaces = SearchableDocumentsField(required=False, help_text="Any Internet-Drafts that this document replaces (approval required for replacing an Internet-Draft you are not the author of)")
+    replaces = SearchableDocumentsField(required=False, help_text='An I-D submission will be automatically attached to the previous version of the I-D with the same name, or assigned "-00" version if no previous version exists. If this submission is intended to replace an I-D with a different name (e.g. when an individual I-D is adopted as a Working Group document), please enter that name here. (Approval required to replace an I-D for which you are not an author.)')
 
     def __init__(self, *args, **kwargs):
         self.name = kwargs.pop("name")