fix gridder URL

Dockerfile

@@ -13,7 +13,7 @@ RUN apt-get update && apt-get install -y \
     python3-mpi4py python3-matplotlib \
   # more optional NIFTy dependencies
   && pip3 install git+https://gitlab.mpcdf.mpg.de/ift/pyHealpix.git \
-  && pip3 install git+https://gitlab.mpcdf.mpg.de/ift/nifty_gridder.git@better_params \
+  && pip3 install git+https://gitlab.mpcdf.mpg.de/ift/nifty_gridder.git \
   && pip3 install git+https://gitlab.mpcdf.mpg.de/mtr/pypocketfft.git \
   && pip3 install jupyter \
   && rm -rf /var/lib/apt/lists/*