[3.13] Disable inputrc in test_pyrepl basic REPL output test (GH-157938)

Specifically, `test_no_newline` would fail if the user's `~/.inputrc`
sets `editing-mode vi`, which adds `(ins)` for "insert mode" to the
beginning of the prompt.
(cherry picked from commit d5dede7)

Co-authored-by: Zachary Ware <zach@python.org>

Author: miss-islington

Lib/test/test_pyrepl/test_pyrepl.py

@@ -1418,6 +1418,8 @@ def test_no_newline(self):
         env = os.environ.copy()
         env.pop("PYTHON_BASIC_REPL", "")
         env["PYTHON_BASIC_REPL"] = "1"
+        # Ensure user's .inputrc doesn't interfere with basic REPL output
+        env["INPUTRC"] = "/dev/null"
 
         commands = "print('Something pretty long', end='')\nexit()\n"
         expected_output_sequence = "Something pretty long>>> exit()"