information mismatch in s4/models/s4/experiments.md

[llk15]

in this .md file, it is shown that, to run the latest LRA results, the commands are:

python -m train experiment=lra/s4-lra-listops
python -m train experiment=lra/s4-lra-imdb
python -m train experiment=lra/s4-lra-cifar
python -m train experiment=lra/s4-lra-aan
python -m train experiment=lra/s4-lra-pathfinder
python -m train experiment=lra/s4-lra-pathx

However, they mismatch with the filenames in s4/configs/experiment/lra, and the correct commands should be:

python -m train experiment=lra/s4-listops
python -m train experiment=lra/s4-imdb
python -m train experiment=lra/s4-cifar
python -m train experiment=lra/s4-aan
python -m train experiment=lra/s4-pathfinder
python -m train experiment=lra/s4-pathx