docs(seed): remove outdated async-await comments (#123)

`async-await` has been blessed by the Almighty Curriculum, and no longer needs to be treated as something new and strange to students.

Author: fterdal

script/seed.js

@@ -3,29 +3,15 @@
 const db = require('../server/db')
 const {User} = require('../server/db/models')
 
-/**
- * Welcome to the seed file! This seed file uses a newer language feature called...
- *
- *                  -=-= ASYNC...AWAIT -=-=
- *
- * Async-await is a joy to use! Read more about it in the MDN docs:
- *
- * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function
- *
- * Now that you've got the main idea, check it out in practice below!
- */
-
 async function seed() {
   await db.sync({force: true})
   console.log('db synced!')
-  // Whoa! Because we `await` the promise that db.sync returns, the next line will not be
-  // executed until that promise resolves!
+
   const users = await Promise.all([
     User.create({email: '[email protected]', password: '123'}),
     User.create({email: '[email protected]', password: '123'})
   ])
-  // Wowzers! We can even `await` on the right-hand side of the assignment operator
-  // and store the result that the promise resolves to in a variable! This is nice!
+
   console.log(`seeded ${users.length} users`)
   console.log(`seeded successfully`)
 }