DESIGN-DOC: Remove reference to outdated google doc

People are asking for permission to that outdated document. Instead of
wasting everyone's time, remove it.

BUG=none
TEST=none

Change-Id: I1606daa26d7d70f7114b4842a10b01d5655d206c
Reviewed-on: https://chromium-review.googlesource.com/566385
Commit-Queue: Stéphane Marchesin <marcheu@chromium.org>
Tested-by: Stéphane Marchesin <marcheu@chromium.org>
Reviewed-by: Ilja H. Friedel <ihf@chromium.org>
diff --git a/DESIGN-DOC.md b/DESIGN-DOC.md
index d5ac14d..97b1038 100644
--- a/DESIGN-DOC.md
+++ b/DESIGN-DOC.md
@@ -1,4 +1,3 @@
-Note: This is an exported copy of https://docs.google.com/a/google.com/document/d/1DYEqfg3v-tITx28kciMb6mNAOeTfy2bIRsnhx9OtQwQ/preview
 [TOC]
 
 # Frecon, a console for freon