ci: enable unittests on macos-14

Add more filters so that LuaJIT can parse headers on macOS 14.

The system headers use a style of enum introduced in C++11 (and allowed
as an extension in C by clang) of the form:

    enum Name : Type {

The system headers also use bitfields in the mach_vm_range_recipe* types:

    struct Foo { int bar : 32; }

Neither of these constructs can be parsed by LuaJIT, so filter the lines
out. Neither of these declarations are used by neovim's unittests.

There is a (now closed) issue about bitfields for LuaJIT:

    https://github.com/LuaJIT/LuaJIT/issues/951

Fixes #26145.

test/unit/testutil.lua

@@ -146,6 +146,9 @@ local function filter_complex_blocks(body)
         or string.find(line, 'value_init_')
         or string.find(line, 'UUID_NULL') -- static const uuid_t UUID_NULL = {...}
         or string.find(line, 'inline _Bool')
+        -- used by macOS headers
+        or string.find(line, 'typedef enum : ')
+        or string.find(line, 'mach_vm_range_recipe')
       )
     then
       result[#result + 1] = line