Browsertests: Rename expectations

Accordingly to new version of RSpec_expections we could no longer use
"be_true", "be_false" and "should" keywords.

Bug: 66184
Change-Id: Ia180a22560b4d56c86b892887c3ebebfbdc466ae
(cherry picked from commit f310993562034e52038c0458cb323e94bcb73197)