index-pack: use strip_suffix to avoid magic numbers

diff --git a/RelNotes b/RelNotes
index 2e4322a073d72f242a56bc2e00c9aa84ff73806c..7879c7dc372705f06decbd745dec7fe1fad1b428 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes/1.7.0.9.txt
\ No newline at end of file
+Documentation/RelNotes/2.0.1.txt
\ No newline at end of file