Merge #16665: scripts: move update-translations.py to maintainer-tools repo

3d50fe2c1f scripts: move update-translations.py to maintainer-tools repo (fanquake)

Pull request description:

  As mentioned in [#16644](https://github.com/bitcoin/bitcoin/pull/16644#issuecomment-522481111), move the `update-translations.py` script out of the `bitcoin/bitcoin` repo. This script is run infrequently by maintainers, and aside from #16644, doesn't see many changes. If it is going to be changed, it probably shouldn't consume review bandwidth in bitcoin/bitcoin anyways.

  PR adding the script to the maintainer-tools repo: https://github.com/bitcoin-core/bitcoin-maintainer-tools/pull/31

  Could also move some other scripts, such as [`gen-manpages.sh`](https://github.com/bitcoin/bitcoin/blob/master/contrib/devtools/gen-manpages.sh).

ACKs for top commit:
  laanwj:
    ACK 3d50fe2c1f

Tree-SHA512: b68da68e2df0c1b3275729890a02726af602eb398507f0a03387a313a73e7629a06db57f3472a1dbcf9e11506e88a8f5f725a397a9ce6afef7627188c88d3d48

doc/translation_process.md

@@ -65,9 +65,9 @@ username = USERNAME
 The Transifex Bitcoin project config file is included as part of the repo. It can be found at `.tx/config`, however you shouldn’t need to change anything.
 
 ### Synchronising translations
-To assist in updating translations, we have created a script to help.
+To assist in updating translations, a helper script is available in the [maintainer-tools repo](https://github.com/bitcoin-core/bitcoin-maintainer-tools).
 
-1. `python contrib/devtools/update-translations.py`
+1. `python3 ../bitcoin-maintainer-tools/update-translations.py`
 2. `git add` new translations from `src/qt/locale/`
 3. Update `src/qt/bitcoin_locale.qrc` manually or via
 ```bash