src/db/tables/featureFlags.ts uses `modified_at` whereas other tables use `updated_at`

Pretty tiny nit, but… was randomly trying to grep for knex+.update() statements without an updated_at column, but came across something possibly odd.

git grep -P -A6 "\.update\(" | grep -Eo "\s[a-z_]+_at: knex.fn.now\(\)" | sort | uniq -c
   1  deleted_at: knex.fn.now()
   6  modified_at: knex.fn.now()
  18  updated_at: knex.fn.now()

Looks like the majority of .update() queries are using an updated_at column, it looks like featureFlags.ts might be an outlier w/ modified_at:

git grep -P -A6 "\.update\(" | grep -E "\s[a-z_]+_at: knex.fn.now\(\)" | sort | uniq -c
   1 src/db/tables/emailAddresses.js-            updated_at: knex.fn.now()
   2 src/db/tables/emailAddresses.js-      updated_at: knex.fn.now()
   1 src/db/tables/emailAddresses.js-      updated_at: knex.fn.now(),
   1 src/db/tables/featureFlags.ts-      deleted_at: knex.fn.now(),
   6 src/db/tables/featureFlags.ts-      modified_at: knex.fn.now(),
   1 src/db/tables/onerep_scans.ts-      updated_at: knex.fn.now(),
   2 src/db/tables/onerep_scans.ts-    updated_at: knex.fn.now(),
   2 src/db/tables/subscribers.js-        updated_at: knex.fn.now(),
   9 src/db/tables/subscribers.js-      updated_at: knex.fn.now(),

Conversely, we can grep by knex.fn.now():

git grep -Po "\b[a-z_]+: knex.fn.now\(\)" src/db/tables | grep -v "ts-ignore" | sort | uniq -c
   4 src/db/tables/emailAddresses.js:updated_at: knex.fn.now()
   1 src/db/tables/featureFlags.ts:deleted_at: knex.fn.now()
   6 src/db/tables/featureFlags.ts:modified_at: knex.fn.now()
   1 src/db/tables/onerep_profiles.ts:created_at: knex.fn.now()
   2 src/db/tables/onerep_scans.ts:created_at: knex.fn.now()
   3 src/db/tables/onerep_scans.ts:updated_at: knex.fn.now()
  12 src/db/tables/subscribers.js:updated_at: knex.fn.now()

┆Issue is synchronized with this Jira Task

Start with src/db/tables/featureFlags.ts and compare its knex update calls with the updated_at usage in src/db/tables/emailAddresses.js, src/db/tables/onerep_scans.ts, and src/db/tables/subscribers.js. Use the grep commands in the issue to verify the inconsistency and confirm whether feature flags should use the same timestamp column; done means the table's timestamp naming is consistent with the intended schema.