convert/svn: remove dead code from entry deletion code path
It was made obsolete when multi-branches commit were split into multiple
Mercurial commits.
adding a
now at: a.patch
applying b.patch
applying c.patch
now at: c.patch
now at: b.patch
% Using index
now at: a.patch
applying b.patch
applying c.patch
now at: c.patch
% No warnings when using index
now at: b.patch
applying c.patch
applying bug314159
now at: bug314159
% Detect ambiguous non-index
patch name "14" is ambiguous:
bug314159
bug141421
abort: patch 14 not in series