[vte] test: Add some more explanation to the UTF-8-test.txt file

[Christian Persch <chpe src gnome org>]

commit f524b6959c760390c0ff5e1d0faef211aa283e26
Author: Christian Persch <chpe src gnome org>
Date:   Wed Oct 16 12:30:44 2019 +0200

    test: Add some more explanation to the UTF-8-test.txt file

 perf/UTF-8-test.txt | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/perf/UTF-8-test.txt b/perf/UTF-8-test.txt
index 47038dcb..fa1c506d 100644
--- a/perf/UTF-8-test.txt
+++ b/perf/UTF-8-test.txt
@@ -7,7 +7,9 @@ Markus Kuhn <http://www.cl.cam.ac.uk/~mgk25/> - 2015-08-28 - CC BY 4.0
 by changing the right margin so that when it is cat(1)ed in a terminal
 emulator whose UTF-8 decoder implements the whatwg Encoding Spec
 [https://encoding.spec.whatwg.org/], the right margin is correctly
-aligned. -- @chpe]
+aligned.  No other changes were made, not even to correct the text
+explaining what you should see; so in some instance that text is now
+incorrect.  -- @chpe]
 
 This test file can help you examine, how your UTF-8 decoder handles
 various types of correct, malformed, or otherwise interesting UTF-8