cleanup: remove useless re-raises of KeyboardInterrupt

KeyboardInterrupt is no longer a subclass of Exception since Python 2.5.

https://docs.python.org/2/whatsnew/2.5.html#pep-352-exceptions-as-new-style-classes

mercurial/branchmap.py

@@ -67,8 +67,6 b' def read(repo):'
             partial.setdefault(label, []).append(node)
             if state == 'c':
                 partial._closednodes.add(node)
-    except KeyboardInterrupt:
-        raise
     except Exception as inst:
         if repo.ui.debugflag:
             msg = 'invalid branchheads cache'

mercurial/extensions.py

@@ -171,8 +171,6 b' def loadall(ui):'
                 continue
         try:
             load(ui, name, path)
-        except KeyboardInterrupt:
-            raise
         except Exception as inst:
             inst = _forbytes(inst)
             if path: