patch 8.2.1183: assert_fails() checks the last error message

Problem:    assert_fails() checks the last error message.
Solution:   Check the first error, it is more relevant.  Fix all the tests
            that rely on the old behavior.
diff --git a/src/testdir/test_trycatch.vim b/src/testdir/test_trycatch.vim
index 68ab7fc..1f1681f 100644
--- a/src/testdir/test_trycatch.vim
+++ b/src/testdir/test_trycatch.vim
@@ -2000,7 +2000,7 @@
 func Test_try_catch_errors()
   call assert_fails('throw |', 'E471:')
   call assert_fails("throw \n ", 'E471:')
-  call assert_fails('catch abc', 'E603:')
+  call assert_fails('catch abc', 'E654:')
   call assert_fails('try | let i = 1| finally | catch | endtry', 'E604:')
   call assert_fails('finally', 'E606:')
   call assert_fails('try | finally | finally | endtry', 'E607:')