hydra.sql: Update comment on regeneration

Dependencies

• [2] CZF3PDJN hydra.sql: embed some in-line docs about schema changes
• [3] SB2V735V Keep track of the database schema version
• [4] N22GPKYT * Put info about logs / build products in the DB.

Change contents

• replacement in src/sql/hydra.sql at line 5
  [2.109]→[2.109:182](∅→∅)
  − -- 2. Run `make -C src/sql update-dbix hydra-postgresql.sql` in the root
  [2.109]

  [2.182]
  + -- 2. Run `make -C src/sql update-dbix` in the root