Remove use of (@z) array flag, which is unsupported in ZSH 5.0

Fixes #7

tests/assertions/in.zunit

@@ -9,5 +9,5 @@
 @test 'Test _zunit_assert_in failure' {
   run assert 'a' in 'x' 'y' 'z'
   assert $state equals 1
-  assert $output same_as "'a' is not in (x ; y ; z)"
+  assert $output same_as "'a' is not in (x y z)"
 }

tests/assertions/not_in.zunit

@@ -9,5 +9,5 @@
 @test 'Test _zunit_assert_not_in failure' {
   run assert 'a' not_in 'a' 'b' 'c'
   assert $state equals 1
-  assert $output same_as "'a' is in (a ; b ; c)"
+  assert $output same_as "'a' is in (a b c)"
 }

zunit

@@ -114,7 +114,7 @@ function _zunit_assert_in() {
 
   [[ $found -eq 1 ]] && return 0
 
-  echo "'$value' is not in (${(@z)array})"
+  echo "'$value' is not in (${(@f)array})"
   exit 1
 }
 
@@ -132,7 +132,7 @@ function _zunit_assert_not_in() {
 
   [[ $found -eq 0 ]] && return 0
 
-  echo "'$value' is in (${(@z)array})"
+  echo "'$value' is in (${(@f)array})"
   exit 1
 }