Update peps/pep-0757.rst

Co-authored-by: Gregory P. Smith <[email protected]>

Author: skirpichev

peps/pep-0757.rst

@@ -472,7 +472,7 @@ implementation).
 Drop :c:member:`~PyLongExport.value` field from the export API
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-With this suggestion, only one export type will exists (array of "digits").  If
+With this suggestion, only one export type will exist (array of "digits").  If
 such view is not available for a given integer, it will be either emulated by
 export functions or the :c:func:`PyLong_Export` will return an error.  In both
 cases, it's assumed that users will use other C-API functions to get "small