tests: Fix an XFail test expectation.

Before this commit, the test was unable to XPass, since there is no
highlighting style called "normal".

Author: danielshahaf

highlighters/main/test-data/precommand-killing2.zsh

@@ -35,5 +35,5 @@ BUFFER='sudo -e /does/not/exist'
 expected_region_highlight=(
   '1 4 precommand' # sudo
   '6 7 single-hyphen-option' # -e
-  '9 23 normal "issue #678"' # /does/not/exist
+  '9 23 default "issue #678"' # /does/not/exist
 )