chore: use `String.to_atom/1` #151

Job	Run time
ash-ci / mix deps.get	17s
ash-ci / audit	37s
ash-ci / MIX_ENV=test mix.compile	3m 51s
ash-ci / MIX_ENV=dev mix.compile	20s
ash-ci / mix docs	34s
ash-ci / Deploy docs to GitHub pages.	7s
ash-ci / mix format --check-formatted	30s
ash-ci / mix sobelow	32s
ash-ci / mix credo --strict	21s
ash-ci / mix dialyzer	3m 4s
ash-ci / mix spark.cheat_sheets --check	23s
ash-ci / mix spark.formatter --check	37s
ash-ci / mix test	46s
ash-ci / mix deps.unlock --check-unused	23s
ash-ci / Release	0s
	12m 22s

Provide feedback