Add rename-subframe-goback to FlagExpectations for PlzNav

After https://codereview.chromium.org/2317203002 and
https://build.chromium.org/p/chromium.fyi/builders/Browser%20Side%20Navigation%20Linux/builds/21220

BUG=607205,575210
TBR=clamy@chromium.org

Review-Url: https://codereview.chromium.org/2336393002
Cr-Commit-Position: refs/heads/master@{#418842}
1 file changed