patch 8.0.0478: tests use assert_true(0) and assert_false(1) to report errors

Problem:    Tests use assert_true(0) and assert_false(1) to report errors.
Solution:   Use assert_report().
diff --git a/src/testdir/test_cscope.vim b/src/testdir/test_cscope.vim
index 4e78faa..4d776e9 100644
--- a/src/testdir/test_cscope.vim
+++ b/src/testdir/test_cscope.vim
@@ -28,7 +28,7 @@
       cscope add Xcscope.out
       set cscopeverbose
     catch
-      call assert_true(0)
+      call assert_report('exception thrown')
     endtry
     call assert_fails('cscope add', 'E560')
     call assert_fails('cscope add Xcscope.out', 'E568')