delete unused images

cf367a53 · ranqiu · 8e731014 · 8e731014 · 8e731014 · 8e731014
4 changed file
--- a/doc/design/images/duplicate_op.graffle
+++ b/doc/design/images/duplicate_op.graffle
--- a/doc/design/images/duplicate_op.png
+++ b/doc/design/images/duplicate_op.png
--- a/doc/design/images/duplicate_op2.graffle
+++ b/doc/design/images/duplicate_op2.graffle
--- a/doc/design/images/duplicate_op2.png
+++ b/doc/design/images/duplicate_op2.png