Stop disabling -Wattributes

In one of the reviews one of the LLMs noticed that the pragma is set but
never unset, so it remains in effect for the rest of the translation
unit. From the comment, it's not clear how old those "old compilers" were,
so let's try if things work without this workaround.

src/basic/static-destruct.h

@@ -12,8 +12,6 @@ typedef void (*free_func_t)(void *p);
  * variables declared in .so's, as the list is private to the same linking unit. But maybe that's a good thing. */
 
 #define _common_static_destruct_attrs_                                  \
-        /* Older compilers don't know "retain" attribute. */            \
-        _Pragma("GCC diagnostic ignored \"-Wattributes\"")              \
         /* The actual destructor structure we place in a special section to find it. */ \
         _section_("SYSTEMD_STATIC_DESTRUCT")                            \
         /* Use pointer alignment, since that is apparently what gcc does for static variables. */ \

src/libsystemd/sd-bus/bus-error.h

@@ -31,12 +31,10 @@ const char* _bus_error_message(const sd_bus_error *e, int error, char buf[static
  * the error map is really added to the final binary.
  *
  * In addition, set the retain attribute so that the section cannot be
- * discarded by ld --gc-sections -z start-stop-gc. Older compilers would
- * warn for the unknown attribute, so just disable -Wattributes.
+ * discarded by ld --gc-sections -z start-stop-gc.
  */
 
 #define BUS_ERROR_MAP_ELF_REGISTER                                      \
-        _Pragma("GCC diagnostic ignored \"-Wattributes\"")              \
         _section_("SYSTEMD_BUS_ERROR_MAP")                              \
         _used_                                                          \
         _retain_                                                        \

src/shared/tests.h

@@ -101,7 +101,6 @@ typedef struct TestFunc {
 
 /* See static-destruct.h for an explanation of how this works. */
 #define REGISTER_TEST(func, ...)                                                                        \
-        _Pragma("GCC diagnostic ignored \"-Wattributes\"")                                              \
         _section_("SYSTEMD_TEST_TABLE") _alignptr_ _used_ _retain_ _variable_no_sanitize_address_       \
         static const TestFunc UNIQ_T(static_test_table_entry, UNIQ) = {                                 \
                 .f = (union f) &(func),                                                                 \