docs: Clarified behavior of TypedArray.getBoolean()

Doc currently says "The method will return whether [the attribute] is equal to zero", which could be read as "returns true if the attribute is zero", which is incorrect. Rephrased as: "...returns false if the attribute is equal to zero, and true otherwise."

Change-Id: Ie7d763ac2784ecc3a7fb522b4fa583ec8d2644d4
BUG: 143049875
Test: make ds-docs