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/shared/securebits-util.c

@@ -42,7 +42,7 @@ int secure_bits_from_string(const char *s) {
         for (p = s;;) {
                 _cleanup_free_ char *word = NULL;
 
-                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)