Fix typo in test's docstring (GH-17856)

* Fix typo in test's docstring. contination -> continuation.
diff --git a/Lib/test/test_eof.py b/Lib/test/test_eof.py
index a091cea..9ef8eb1 100644
--- a/Lib/test/test_eof.py
+++ b/Lib/test/test_eof.py
@@ -27,7 +27,7 @@
             raise support.TestFailed
 
     def test_line_continuation_EOF(self):
-        """A contination at the end of input must be an error; bpo2180."""
+        """A continuation at the end of input must be an error; bpo2180."""
         expect = 'unexpected EOF while parsing (<string>, line 1)'
         with self.assertRaises(SyntaxError) as excinfo:
             exec('x = 5\\')