journald-server: drop invalid assert()

config_parse_compress() is not used for parsing unit files, hence unit
is always NULL.

Fixes #32856

Follow-up-for: 6813be2eba

src/journal/journald-server.c

@@ -3012,7 +3012,6 @@ int config_parse_compress(
         JournalCompressOptions* compress = ASSERT_PTR(data);
         int r;
 
-        assert(unit);
         assert(filename);
         assert(rvalue);