Clean out unused tor connect strings

Some of the tor connect strings for android were added in anticipation, but didn't end up being used in the 14.5 implementation, so are still unused. E.g. connection_assist_try_a_bridge_learn_more_error_code. After we settle on the wording in #43606 and complete the features for 15.0 we should go through and remove the strings that ended up unused.

Moreover, we should backport this to 14.5 so that the strings get removed from our translation repository when neither version needs them any more.