git-completion.bash: replace zsh notation that breaks bash 3.X

diff --git a/RelNotes b/RelNotes
index 63941cdfa9b8c7b3c4e693085a53928f863959db..5964e1c4ca69a74cffebfbd27f693acce5d26cbc 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes-1.5.0.1.txt
\ No newline at end of file
+Documentation/RelNotes/1.8.1.1.txt
\ No newline at end of file