erp5testnode/testsuite: switch to buildout.hash.cfg

This was missing in this software and in 03c5b311 (Stop using
hexagonit.recipe.download, 2021-12-03) the hash got out of sync

software/erp5testnode/testsuite/buildout.hash.cfg

+# THIS IS NOT A BUILDOUT FILE, despite purposedly using a compatible syntax.
+# The only allowed lines here are (regexes):
+# - "^#" comments, copied verbatim
+# - "^[" section beginings, copied verbatim
+# - lines containing an "=" sign which must fit in the following categorie.
+#   - "^\s*filename\s*=\s*path\s*$" where "path" is relative to this file
+#     Copied verbatim.
+#   - "^\s*hashtype\s*=.*" where "hashtype" is one of the values supported
+#     by the re-generation script.
+#     Re-generated.
+# - other lines are copied verbatim
+# Substitution (${...:...}), extension ([buildout] extends = ...) and
+# section inheritance (< = ...) are NOT supported (but you should really
+# not need these here).
+
+[template-erp5testnode]
+filename = instance.cfg.in
+md5sum = bbfe2f0e83df4d6cd2120c0ef3c483cd

software/erp5testnode/testsuite/testsuite.cfg

+[buildout]
+extends = buildout.hash.cfg
+
 [template-erp5testnode]
 recipe = slapos.recipe.template
 url = ${:_profile_base_location_}/instance.cfg.in
-md5sum = d864a32edab3c4f7207a7d4fe6bb7e30
 output = ${buildout:directory}/template.cfg
 
 [template]