[PATCH] tests: fix test-casefolding.t

[Simon Farnsworth]

# HG changeset patch
# User Simon Farnsworth <simonfar at fb.com>
# Date 1477063876 -3600
#      Fri Oct 21 16:31:16 2016 +0100
# Node ID 1e6f773db8acf006cbfd09205b57e70252faafb8
# Parent  260af19891f2bed679a662be07d1379bb8207592
tests: fix test-casefolding.t

The message had changed, but the test was not updated. This test does not
run on Linux, but failed on my Mac.

diff --git a/tests/test-casefolding.t b/tests/test-casefolding.t
--- a/tests/test-casefolding.t
+++ b/tests/test-casefolding.t
@@ -51,7 +51,8 @@
   $ echo b > D/b
   $ hg ci -Am addb D/b
   $ hg mv D/b d/b
-  D/b: not overwriting - file exists
+  D/b: not overwriting - file already committed
+  (hg rename --force to replace the file by recording a rename)
   $ hg mv D/b d/c
   $ hg st
   A D/c