Rename EXTRACT_QUOTES to EXTRACT_UNQUOTE

Whenever I see EXTRACT_QUOTES, I'm always confused whether it means to
leave the quotes in or to take them out. Let's say "unquote", like we
say "cunescape".

src/basic/cap-list.c

@@ -100,7 +100,7 @@ int capability_set_from_string(const char *s, uint64_t *set) {
                 _cleanup_free_ char *word = NULL;
                 int r;
 
-                r = extract_first_word(&p, &word, NULL, EXTRACT_QUOTES);
+                r = extract_first_word(&p, &word, NULL, EXTRACT_UNQUOTE);
                 if (r == -ENOMEM)
                         return r;
                 if (r <= 0)