Cell: remove unneeded newline in the middle of class documentation

The `contents` documentation was split over multiple lines, but an extra
newline meant that there was an (indented) line with just the word "and"
followed by an unindented line with "further attempts...". Remove that newline
to avoid having just a single word in the documentation and to fix the
indentation.

Author: DanielEScherzer

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.");