go/zodb, go/zodb/btree: Fix go generate after rename on zodbtools side

run_with_zodb3py2_compat was renamed to run_with_zodb4py2_compat in
nexedi/zodbtools@c59a54ca .

Without the fix go genrate was failing as

    (neo) (z-dev) (g.env) kirr@deca:~/src/neo/src/lab.nexedi.com/kirr/neo/go/zodb/btree$ go generate
    Traceback (most recent call last):
      File "./testdata/gen-testdata", line 26, in <module>
        from zodbtools.test.gen_testdata import run_with_zodb3py2_compat
    ImportError: cannot import name run_with_zodb3py2_compat

and

    (neo) (z-dev) (g.env) kirr@deca:~/src/neo/src/lab.nexedi.com/kirr/neo/go/zodb$ go generate
    Traceback (most recent call last):
      File "./py/pydata-gen-testdata", line 24, in <module>
        from zodbtools.test.gen_testdata import run_with_zodb3py2_compat
    ImportError: cannot import name run_with_zodb3py2_compat

This amends commit fc69e00d (go/zodb/fs1: Fix Python database generator
to work with recent zodbtools).

go/zodb/btree/testdata/gen-testdata

 #!/usr/bin/env python2
 # -*- coding: utf-8 -*-
-# Copyright (C) 2018-2020  Nexedi SA and Contributors.
+# Copyright (C) 2018-2021  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
@@ -23,7 +23,7 @@
 from ZODB.DB import DB
 from BTrees.LOBTree import LOBucket, LOBTree
 from ZODB.utils import u64
-from zodbtools.test.gen_testdata import run_with_zodb3py2_compat
+from zodbtools.test.gen_testdata import run_with_zodb4py2_compat
 import os, os.path, transaction
 
 from golang.gcompat import qq
@@ -89,7 +89,7 @@ def main2():
     db.close()
 
 def main():
-    run_with_zodb3py2_compat(main2)
+    run_with_zodb4py2_compat(main2)
 
 
 if __name__ == '__main__':

go/zodb/py/pydata-gen-testdata

 #!/usr/bin/env python2
 # -*- coding: utf-8 -*-
-# Copyright (C) 2017-2020  Nexedi SA and Contributors.
+# Copyright (C) 2017-2021  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
@@ -21,7 +21,7 @@
 """generate reference pickle objects encoding for tests"""
 
 from ZODB import serialize
-from zodbtools.test.gen_testdata import run_with_zodb3py2_compat
+from zodbtools.test.gen_testdata import run_with_zodb4py2_compat
 from golang.gcompat import qq
 
 def main2():
@@ -56,7 +56,7 @@ def main2():
         emit("}")
 
 def main():
-    run_with_zodb3py2_compat(main2)
+    run_with_zodb4py2_compat(main2)
 
 if __name__ == '__main__':
     main()