[3.15] Fix a stray newline in the cell type docstring (GH-157240) (#157278)

Co-authored-by: Daniel Scherzer <daniel.e.scherzer@gmail.com>

Author: miss-islington

Objects/cellobject.c

@@ -29,7 +29,7 @@ PyDoc_STRVAR(cell_new_doc,
 "\n"
 "  contents\n"
 "    the contents of the cell. If not specified, the cell will be empty,\n"
-"    and \n further attempts to access its cell_contents attribute will\n"
+"    and further attempts to access its cell_contents attribute will\n"
 "    raise a ValueError.");