[gdb/python] Fix typo in test_python

Fix typo in ref_output_0 variable in test_python.

Tested by running the selftest on x86_64-linux with python 3.11.

---
 gdb/python/python.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gdb/python/python.c b/gdb/python/python.c
index c0312413a73..c7d4157b70c 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -2242,7 +2242,7 @@ test_python ()
     SELF_CHECK (saw_exception);
     std::string ref_output_0 ("Traceback (most recent call last):\n"
 			      "  File \"<string>\", line 0, in <module>\n"
-			      " KeyboardInterrupt\n");
+			      "KeyboardInterrupt\n");
     std::string ref_output_1 ("Traceback (most recent call last):\n"
 			      "  File \"<string>\", line 1, in <module>\n"
 			      "KeyboardInterrupt\n");