[3.9] bpo-43776: Remove list call from args in Popen repr (GH-25338) (GH-26510)

Removes the `list` call in the Popen `repr`.

Current implementation:

For cmd = `python --version`,  with `shell=True`.

```bash
<Popen: returncode: None args: ['p', 'y', 't', 'h', 'o', 'n', ' ', '-', '-',...>
```

For `shell=False` and args=`['python', '--version']`, the output is correct:

```bash
<Popen: returncode: None args: ['python', '--version']>
```

With the new changes the `repr`  yields:

For cmd = `python --version`,  with `shell=True`:

```bash
<Popen: returncode: None args: 'python --version'>
```

For `shell=False` and args=`['python', '--version']`, the output:

```bash
<Popen: returncode: None args: ['python', '--version']>
```

Automerge-Triggered-By: GH:gpshead.
(cherry picked from commit db0c5b786d)

Co-authored-by: M. Kocher <michael.kocher@me.com>

Co-authored-by: M. Kocher <michael.kocher@me.com>

Lib/subprocess.py

@@ -989,7 +989,7 @@ class Popen(object):
     def __repr__(self):
         obj_repr = (
             f"<{self.__class__.__name__}: "
-            f"returncode: {self.returncode} args: {list(self.args)!r}>"
+            f"returncode: {self.returncode} args: {self.args!r}>"
         )
         if len(obj_repr) > 80:
             obj_repr = obj_repr[:76] + "...>"