Fix a long-standing bug in a unit test. This uncovers a regression.

The test never actually defined a function named 'alias1', not even
when zsh 5.4 warned it about this (see 9523d6d49c,
which was wrong and is hereby reverted).

The test that's now failing has been filed as issue #558.

highlighters/main/test-data/alias.zsh

@@ -29,10 +29,7 @@
 
 alias alias1="unused expansion"
 alias -s alias2="echo"
-if set -o | grep -q aliasfuncdef; then
-  setopt alias_func_def # 5.4+
-fi
-alias1() {} # to check that it's highlighted as an alias, not as a function
+function alias1() {} # to check that it's highlighted as an alias, not as a function
 
 BUFFER='x.alias2; alias1'
 
@@ -50,5 +47,5 @@ if zmodload -e zsh/parameter || [[ "$(type -w x.alias2)" == *suffix* ]]; then
 fi
 expected_region_highlight+=(
   "9 9 commandseparator" # ;
-  "11 16 alias" # alias1
+  "11 16 alias 'issue #558'" # alias1
 )