Exclude old files from mypy

[ns-rse]

Currently the mypy hook checks all .py files and there are a lot of errors reported for pipeline_slam3UIs.py and
all_introns_count_and_info.py. It should be possible to exclude these under [tool.mypy] with the following although
it isn't currently recognised...

[tool.mypy]
exclude = [
  '^all_introns_counts_and_info\.py$',
  '^pipeline_slam_3UIs\.py$',
]

Single quotes are used to give string literals and avoid the need to escape characters in regular expressions in TOML
files (see note in example).