Remove unmaintained transifex-client

Transifex recommends using their `tx` CLI that can be downloaded as a
standalone application: https://github.com/transifex/cli

.tx/config

@@ -1,20 +1,20 @@
 [main]
 host = https://www.transifex.com
 
-[indico.core-messages-react]
+[o:indico:p:indico:r:core-messages-react]
 file_filter = indico/translations/<lang>/LC_MESSAGES/messages-react.po
 source_file = indico/translations/messages-react.pot
 source_lang = en
-type = PO
+type        = PO
 
-[indico.core-messages-js]
+[o:indico:p:indico:r:core-messages-js]
 file_filter = indico/translations/<lang>/LC_MESSAGES/messages-js.po
 source_file = indico/translations/messages-js.pot
 source_lang = en
-type = PO
+type        = PO
 
-[indico.core-messages]
+[o:indico:p:indico:r:core-messages]
 file_filter = indico/translations/<lang>/LC_MESSAGES/messages.po
 source_file = indico/translations/messages.pot
 source_lang = en
-type = PO
+type        = PO

requirements.dev.in

@@ -23,4 +23,3 @@ sphinx-issues
 sphinx-rtd-theme
 sphinx!=4.0.*  # not compatible with jinja 3 - https://github.com/sphinx-doc/sphinx/issues/9216
 sqlparse
-transifex-client

requirements.dev.txt

@@ -68,10 +68,6 @@ flask-url-map-serializer==0.0.1
     # via -r requirements.dev.in
 freezegun==1.2.1
     # via -r requirements.dev.in
-gitdb==4.0.9
-    # via gitpython
-gitpython==3.1.27
-    # via transifex-client
 greenlet==1.1.2
     # via
     #   -c requirements.txt
@@ -177,8 +173,6 @@ python-dateutil==2.8.2
     # via
     #   -c requirements.txt
     #   freezegun
-python-slugify==4.0.1
-    # via transifex-client
 pytz==2022.1
     # via
     #   -c requirements.txt
@@ -196,7 +190,6 @@ requests==2.28.0
     #   -c requirements.txt
     #   plantweb
     #   sphinx
-    #   transifex-client
 schemainspect==3.1.1652015119
     # via migra
 six==1.16.0
@@ -207,9 +200,6 @@ six==1.16.0
     #   plantweb
     #   python-dateutil
     #   sqlbag
-    #   transifex-client
-smmap==5.0.0
-    # via gitdb
 snowballstemmer==2.2.0
     # via sphinx
 sphinx==5.0.1
@@ -245,8 +235,6 @@ sqlbag==0.1.1617247075
     # via migra
 sqlparse==0.4.2
     # via -r requirements.dev.in
-text-unidecode==1.3
-    # via python-slugify
 tokenize-rt==4.2.1
     # via pyupgrade
 tomli==2.0.1
@@ -256,13 +244,10 @@ tomli==2.0.1
     #   pytest
 tornado==6.1
     # via livereload
-transifex-client==0.14.4
-    # via -r requirements.dev.in
 urllib3==1.26.9
     # via
     #   -c requirements.txt
     #   requests
-    #   transifex-client
 werkzeug==2.1.2
     # via
     #   -c requirements.txt