Remove duplicated lines in Android Build Instruction

In GN args example of Android Build Instruction, 'symbol_level'
and 'enable_incremental_javac' options are duplicated.

BUG=632028

Review-Url: https://codereview.chromium.org/2179943007
Cr-Commit-Position: refs/heads/master@{#418067}
1 file changed