filter-branch: avoid passing commit message through sed

diff --git a/RelNotes b/RelNotes
index ad613ead7bfedefeca6e3e49bc0ba9349702aa44..5696e88ad5f86cac0e7095469e8d705337c91e2e 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes/1.8.1.4.txt
\ No newline at end of file
+Documentation/RelNotes/2.0.5.txt
\ No newline at end of file