diff-index.c: "git diff" has no need to read blob from the standard input

diff --git a/RelNotes b/RelNotes
index 5217e8e5543a696660e3f275d9717e0656d786f8..fb9320b14baeae5fdb759a99e7edb77546cd5bc1 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes-1.7.2.3.txt
\ No newline at end of file
+Documentation/RelNotes/1.7.6.6.txt
\ No newline at end of file