Require exactly 'true' for truthy reference directive prop

[jakebailey]

This is for #57681; noticed that we just say "if it's present it's true" rather than actually requiring the string true. Seems a little weird. No breaks locally, and didn't see much in https://github.com/search?q=%2Fno-default-lib%3D%22%2F+language%3Atypescript&type=code either.

[jakebailey]

@typescript-bot test top200
@typescript-bot user test this
@typescript-bot run dt

[typescript-bot]

Starting jobs; this comment will be updated as builds start and complete.

Command	Status	Results
test top200	✅ Started	✅ Results
user test this	✅ Started	✅ Results
run dt	✅ Started	✅ Results

[typescript-bot]

Hey @jakebailey, the results of running the DT tests are ready.
Everything looks the same!
You can check the log here.

[typescript-bot]

@jakebailey Here are the results of running the user test suite comparing main and refs/pull/57782/merge:

There were infrastructure failures potentially unrelated to your change:

• 1 instance of "Unknown failure"
• 1 instance of "Package install failed"

Otherwise...

Everything looks good!

[typescript-bot]

@jakebailey Here are the results of running the top-repos suite comparing main and refs/pull/57782/merge:

Everything looks good!