t7004-tag.sh: re-arrange git tag comment for clarity

diff --git a/RelNotes b/RelNotes
index 0e11dea6d0d1b888ddfc2825bb197aae8027d459..b942e499449d97aeb50c73ca2bdc1c6e6d528743 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes-1.7.3.txt
\ No newline at end of file
+Documentation/RelNotes/1.7.4.txt
\ No newline at end of file