Issue #1797920 by dcam, izus, Lars Toomre: Remove t() from test asserts in misc system tests

modules/simpletest/tests/theme.test

modules/simpletest/tests/update.test

modules/simpletest/tests/upgrade/update.field.test

modules/simpletest/tests/upgrade/update.trigger.test

modules/simpletest/tests/upgrade/update.user.test

modules/simpletest/tests/upgrade/upgrade.comment.test

modules/simpletest/tests/upgrade/upgrade.filter.test

modules/simpletest/tests/upgrade/upgrade.forum.test

modules/simpletest/tests/upgrade/upgrade.locale.test

modules/simpletest/tests/upgrade/upgrade.menu.test

modules/simpletest/tests/upgrade/upgrade.node.test

modules/simpletest/tests/upgrade/upgrade.poll.test

modules/simpletest/tests/upgrade/upgrade.taxonomy.test

modules/simpletest/tests/upgrade/upgrade.test

modules/simpletest/tests/upgrade/upgrade.translatable.test

modules/simpletest/tests/upgrade/upgrade.trigger.test

modules/simpletest/tests/upgrade/upgrade.upload.test

modules/system/system.test