patch 8.2.3058: 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 ee97e56..563b7ba 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -924,6 +924,13 @@
   CheckDefAndScriptFailure(lines, 'E1172:')
 
   lines =<< trim END
+      var a = 0
+      var b = (a == 0 ? 1 : 2)
+      assert_equal(1, b)
+  END
+  CheckDefAndScriptSuccess(lines)
+
+  lines =<< trim END
       def ShadowLocal()
         var one = 1
         var l = [1, 2, 3]