doc: remove operation based on do_autogen.sh

do_autogen.sh has been deleted by below patch
    commit ea9b972
        remove do_autogen.sh
Signed-off-by: Changcheng Liu <changcheng.liu@intel.com>

doc/dev/corpus.rst

@@ -26,12 +26,6 @@ We can generate an object corpus for a particular version of ceph like so.
 	cd ceph
 	git submodule update --init --recursive
 
-#. Build with flag to dump objects to /tmp/foo::
-
-	rm -rf /tmp/foo ; mkdir /tmp/foo
-	./do_autogen.sh -e /tmp/foo
-	make
-
 #. Start via vstart::
 
 	cd build
@@ -55,11 +49,6 @@ Do some more stuff with rgw if you know how.
 
 	../src/stop.sh
 
-#. Import the corpus (this will take a few minutes)::
-
-	test/encoding/import.sh /tmp/foo `./ceph-dencoder version` ../ceph-object-corpus/archive
-	test/encoding/import-generated.sh ../ceph-object-corpus/archive
-
 #. Prune it!  There will be a bazillion copies of various objects, and we only want a representative sample.::
 
 	pushd ../ceph-object-corpus