patch 8.2.3060: Vim9: cannot use ternary operator in parenthesis

Problem:    Vim9: cannot use ternary operator in parenthesis.
Solution:   Do not use "=~" for a default argument value.  (closes #8462)
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 563b7ba..4816cb6 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -927,6 +927,9 @@
       var a = 0
       var b = (a == 0 ? 1 : 2)
       assert_equal(1, b)
+      var txt = 'a'
+      b = (txt =~ 'x' ? 1 : 2)
+      assert_equal(2, b)
   END
   CheckDefAndScriptSuccess(lines)