doc: Update translation generation instructions

This is a follow-up of bitcoin#31731.

Technically this change fixes the preset configuration
execution failure as it needs multiprocess to be enabled,
so we disable it using -DWITH_MULTIPROCESS=OFF.

This code will need to be updated in PRs bitcoin#31741 and bitcoin#31802.

Author: pablomartin4btc

doc/translation_process.md

@@ -18,7 +18,7 @@ We use automated scripts to help extract translations in both Qt, and non-Qt sou
 
 To automatically regenerate the `bitcoin_en.ts` file, run the following commands:
 ```sh
-cmake --preset dev-mode -DWITH_USDT=OFF
+cmake --preset dev-mode -DWITH_USDT=OFF -DWITH_MULTIPROCESS=OFF
 cmake --build build_dev_mode --target translate
 ```