Fix Unsafe Browser automated test in Farsi

The "The Unsafe Browser can be used in all languages supported in Tails" test suite scenario is failing when the Unsafe Browser is run in Farsi language. Farsi is a RTL language. The opening page displays poorly under RTL languages, so the final dot appears on the left even though the sentence is in English, a LTR language.

This MR avoids the test case to fail removing the dot from the image selection part.