Add a performance todo, remove a duplicate.

TODO.md

diff --git a/TODO.md b/TODO.md
index f7d56b8..6a23f13 100644
--- a/TODO.md
+++ b/TODO.md
@@ -25,13 +25,13 @@
 
 # Features
 
+* performance: read local directory later when copying files from zip to zip
 * set version needed correctly
 * Winzip AES support
   * test cases decryption: <=20, >20, stat for both
   * test cases encryption: no password, default password, file-specific password, 128/192/256, <=20, >20
   * support testing on Linux
   * support testing on macOS
-* xz support
 * consistently use `_zip_crypto_clear()` for passwords
 * implement compression flags for `zip_set_file_compression()`
 * support setting extra fields from `zip_source`