fix typo in builder.ts:32

[Damiencastro]

I'm a novice at angular and I came across this typo. I'll be honest, I'm not 100% how to properly do linter & test stuff, but it's a pretty simple typo that's being fixed. I filled out the CLA, so please let me know if I need to do anything else!

Checklist

• Issue number for this PR: #nnn (required)

•    No issue number for this PR
  

• Docs included?: (yes/no; required for all API/functional changes)

•    No docs included, just a typo I found while debugging
  

• Test units included?: (yes/no; required)

•    No, since it's just a simple typo I'm hoping that I don't have to figure the tests out just yet
  

• In a clean directory, yarn install, yarn test run successfully? (yes/no; required)

•    No, I'll be honest, not sure what this is supposed to be. Sorry for the confusion...
  

Description

Code sample