buildman: Drop comment about Ctrl-C problem

This bug is now fixed, so drop this comment.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/buildman/README b/tools/buildman/README
index 5a709c6..d688b7c 100644
--- a/tools/buildman/README
+++ b/tools/buildman/README
@@ -1169,8 +1169,6 @@
 problems, perhaps by building a few boards for each arch, or checking
 commits for changed files and building only boards which use those files.
 
-A specific problem to fix is that Ctrl-C does not exit buildman cleanly when
-multiple builder threads are active.
 
 Credits
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