Fix typo in android.net.Uri documentation.

This typo has been present since before the "auto import"
of cupcake sources in 2009.

Bug: 114704047
Test: Treehugger
Test: Checked through source inspection that this really returns
      the encoded form: its implementation is ssp.getEncoded(),
      whose implementation in turn is:
      return hasEncoded ? encoded : (encoded = encode(decoded));
Change-Id: I0e4fed702e6b3012429778ccbd18a495a5d69e9f