Remove obsolete note about native CPU byte format

Comment in entry.h said that the cache contents is in the native CPU
byte format, which is really not true anymore for quite some time.

cache.h

@@ -40,10 +40,6 @@ extern char *gitenv_bc(const char *);
 
 /*
  * Basic data structures for the directory cache
- *
- * NOTE NOTE NOTE! This is all in the native CPU byte format. It's
- * not even trying to be portable. It's trying to be efficient. It's
- * just a cache, after all.
  */
 
 #define CACHE_SIGNATURE 0x44495243	/* "DIRC" */