Add --minimum-perc to transifex pull command [ci skip]

docs/topics/project-management.md

@@ -165,7 +165,7 @@ Here's how differences between the old and new source files will be handled:
 When a translator has finished translating their work needs to be downloaded from Transifex into the REST framework repository. To do this, run:
 
     # 3. Pull the translated django.po files from Transifex.
-    tx pull -a
+    tx pull -a --minimum-perc 10
     cd rest_framework
     # 4. Compile the binary .mo files for all supported languages.
     django-admin.py compilemessages