test: enforce generaldelta format with the right option

The option that will become true by default is now 'usegeneraldelta' We have to
adjust the change made in b75fed55f6dc to actually achieve its goal.

tests/test-shelve.t

@@ -971,7 +971,7 b' Shelve from general delta repo uses bund'
 
 no general delta
 
-  $ hg clone --pull repo bundle1 --config format.generaldelta=0
+  $ hg clone --pull repo bundle1 --config format.usegeneraldelta=0
   requesting all changes
   adding changesets
   adding manifests
@@ -991,7 +991,7 b' no general delta'
 
 with general delta
 
-  $ hg clone --pull repo bundle2 --config format.generaldelta=1
+  $ hg clone --pull repo bundle2 --config format.usegeneraldelta=1
   requesting all changes
   adding changesets
   adding manifests