fix tests with the renamed ob-shell.el

  Note, users may have to edit their local.mk files to change the
  value of BTEST_OB_LANGUAGES to remove sh and include shell.

mk/default.mk

@@ -63,7 +63,7 @@ BTEST	= $(BATCH) \
 	  --eval '(setq \
 		org-batch-test t \
 		org-babel-load-languages \
-	          (quote ($(foreach ob-lang,$(BTEST_OB_LANGUAGES) emacs-lisp sh org,$(lst-ob-lang)))) \
+	          (quote ($(foreach ob-lang,$(BTEST_OB_LANGUAGES) emacs-lisp shell org,$(lst-ob-lang)))) \
 	    org-test-select-re "$(BTEST_RE)" \
 	  )' \
 	  -l org-loaddefs.el \