Update taiga backend

Dockerfile

@@ -15,7 +15,7 @@ RUN apt-get update && apt-get install -y \
 # We don't use release tags but the stable branches
 
 ## backend (https://github.com/taigaio/taiga-back/commits/stable)
-RUN curl -L https://github.com/taigaio/taiga-back/archive/ece8bb7ce64258da98713319f05590687506b1aa.tar.gz | tar -xz -C /app/code/taiga-back --strip-components 1 -f -
+RUN curl -L https://github.com/taigaio/taiga-back/archive/34fbb01fe0dac0f05f884891d43f1cb48f2c1a75.tar.gz | tar -xz -C /app/code/taiga-back --strip-components 1 -f -
 
 ## frontend (https://github.com/taigaio/taiga-front-dist/commits/stable)
 RUN curl -L https://github.com/taigaio/taiga-front-dist/archive/ac88fa2f9127c26173c2dd04e59dd076a3899ab9.tar.gz | tar -xz -C /app/code/taiga-front-dist --strip-components 1 -f -