Get rid of redundant include directives from TextIterator.cpp

This patch gets rid of redundant include directives from "TextIterator.cpp"
for improving code health.

BUG=n/a
TEST=n/a; no behavior changes

Review-Url: https://codereview.chromium.org/2909263002
Cr-Commit-Position: refs/heads/master@{#475476}
1 file changed