Cosmetic fixes for whitespace and a regex in packaging.

The goal of the regex is to catch a (alpha), b (beta), c or rc
(release candidate), so the existing pattern puzzled me. Tests were
OK before and after the change.
diff --git a/Lib/packaging/version.py b/Lib/packaging/version.py
index 0eaf80b..7d812bb 100644
--- a/Lib/packaging/version.py
+++ b/Lib/packaging/version.py
@@ -253,7 +253,7 @@
     # if we have something like "b-2" or "a.2" at the end of the
     # version, that is pobably beta, alpha, etc
     # let's remove the dash or dot
-    rs = re.sub(r"([abc|rc])[\-\.](\d+)$", r"\1\2", rs)
+    rs = re.sub(r"([abc]|rc)[\-\.](\d+)$", r"\1\2", rs)
 
     # 1.0-dev-r371 -> 1.0.dev371
     # 0.1-dev-r79 -> 0.1.dev79