org-footnote-tag-for-non-org-mode-files

org-footnote-tag-for-non-org-mode-files is a variable defined in `org-footnote.el'.
Its value is

"Footnotes:"

Documentation:
Tag marking the beginning of footnote section.
The Org footnote engine can be used in arbitrary text files as well
as in Org-mode. Outside Org mode, new footnotes are always placed at
the end of the file. When you normalize the notes, any line containing
only this tag will be removed, a new one will be inserted at the end
of the file, followed by the collected and normalized footnotes.

If you don't want any tag in such buffers, set this variable to nil.

You can customize this variable.