Switch to `augur curate titlecase` and `format-dates` subcommands

[j23414]

Description of proposed changes

As part of an ongoing migration of transform scripts to augur curate subcommands, this PR moves to replace the titlecase and format-dates scripts with their corresponding augur curate subcommands:

• augur curate titlecase
• augur curate format-dates

Related issue(s)

Testing

• [x] Checks pass
• [x] cd ingest; nextstrain build --cpus 1 . data/metadata.tsv runs locally