Correct the code example in Python 3.7's What's New (GH-5696)
There was an extra dash in the example for re.sub().
diff --git a/Doc/whatsnew/3.7.rst b/Doc/whatsnew/3.7.rst
index c3761c5..89ca5d7 100644
--- a/Doc/whatsnew/3.7.rst
+++ b/Doc/whatsnew/3.7.rst
@@ -1146,7 +1146,7 @@
:func:`re.sub()` now replaces empty matches adjacent to a previous
non-empty match. For example ``re.sub('x*', '-', 'abxd')`` returns now
- ``'-a-b--d-'`` instead of ``'-a-b--d-'`` (the first minus between 'b' and
+ ``'-a-b--d-'`` instead of ``'-a-b-d-'`` (the first minus between 'b' and
'd' replaces 'x', and the second minus replaces an empty string between
'x' and 'd').