Fix new_startup_env docs

Author: johnslavik

Lib/test/test_repl.py

@@ -70,7 +70,7 @@ def spawn_repl(*args, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, custom=F
 
 @contextmanager
 def new_startup_env(*, code: str, histfile: str = ".pythonhist"):
-    """Create temporary environment variables for a PYTHONSTARTUP script."""
+    """Create environment variables for a PYTHONSTARTUP script in a temporary directory."""
     with os_helper.temp_dir() as tmpdir:
         filename = os.path.join(tmpdir, "pythonstartup.py")
         with open(filename, "w") as f: