Where is a "Sync project with gradle files" button in Android Studio 3?

In Android Studio 3.3 it is here:

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EDIT: They like to keep playing with the toolbar.

Since Android Studio 3.3, the icon has been updated and moved back across to the right:

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Original answer:

It hasn't disappeared. They have just moved it between the Save and Sync files button on the far left end of the toolbar.

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