There's a cleaner way to do this, commit to module formatter pending.

Revert "No longer need to reference 'version_added' in docs for these, as this was quite a while ago."

This reverts commit ff0a41d446.

library/database/mysql_db

@@ -25,7 +25,7 @@ module: mysql_db
 short_description: Add or remove MySQL databases from a remote host.
 description:
    - Add or remove MySQL databases from a remote host.
-version_added: historical
+version_added: "0.6"
 options:
   name:
     description:

library/database/mysql_user

@@ -24,7 +24,7 @@ module: mysql_user
 short_description: Adds or removes a user from a MySQL database.
 description:
    - Adds or removes a user from a MySQL database.
-version_added: historical
+version_added: "0.6"
 options:
   name:
     description:

library/database/postgresql_db

@@ -22,7 +22,7 @@ module: postgresql_db
 short_description: Add or remove PostgreSQL databases from a remote host.
 description:
    - Add or remove PostgreSQL databases from a remote host.
-version_added: historical
+version_added: "0.6"
 options:
   name:
     description:

library/database/postgresql_user

@@ -34,7 +34,7 @@ description:
      the module to try to remove the user, but if not possible keep going; the
      module will report if changes happened and separately if the user was
      removed or not.
-version_added: historical
+version_added: "0.6"
 options:
   name:
     description: