basic/strv: drop strv_free_free

I think the function name is confusing: we generally say "free_free" when
both keys and values are freed in a hash map, but here the type is an
array of strvs, so the name should be something like strv_array_free.

The function is unused since 143fadf369 (2018),
let's just drop it.

src/basic/strv.c

@@ -860,16 +860,6 @@ bool strv_fnmatch_full(char* const* patterns, const char *s, int flags, size_t *
         return false;
 }
 
-char*** strv_free_free(char ***l) {
-        if (!l)
-                return NULL;
-
-        for (char ***i = l; *i; i++)
-                strv_free(*i);
-
-        return mfree(l);
-}
-
 char** strv_skip(char **l, size_t n) {
 
         while (n > 0) {

src/basic/strv.h

@@ -228,9 +228,6 @@ static inline bool strv_fnmatch_or_empty(char* const* patterns, const char *s, i
                strv_fnmatch_full(patterns, s, flags, NULL);
 }
 
-char*** strv_free_free(char ***l);
-DEFINE_TRIVIAL_CLEANUP_FUNC(char***, strv_free_free);
-
 char** strv_skip(char **l, size_t n);
 
 int strv_extend_n(char ***l, const char *value, size_t n);