gh-37062: clean singular interface (full pep8) + use standard open and zip
    
This is

- cleaning for pep8 compliance the `singular` pexpect interface
- making sure to use everywhere the standard `zip` and `open`

### 📝 Checklist

- [x] The title is concise, informative, and self-explanatory.
- [x] The description explains in detail what this PR is about.
    
URL: #37062
Reported by: Frédéric Chapoton
Reviewer(s): David Coudert

Author: Release Manager

src/sage/interfaces/gap.py

@@ -206,7 +206,6 @@
 
 import re
 import os
-import io
 import pexpect
 import time
 import platform
@@ -221,7 +220,7 @@
     # Passing -A allows us to use a minimal GAP installation without
     # producing errors at start-up. The files sage.g and sage.gaprc are
     # used to load any additional packages that may be available.
-    gap_cmd  = f'gap -A -l "{GAP_ROOT_PATHS}"'
+    gap_cmd = f'gap -A -l "{GAP_ROOT_PATHS}"'
     if SAGE_GAP_MEMORY is not None:
         gap_cmd += " -s " + SAGE_GAP_MEMORY + " -o " + SAGE_GAP_MEMORY
 else:
@@ -1320,8 +1319,8 @@ def help(self, s, pager=True):
             sline = int(sline) - 1
             if self.is_remote():
                 self._get_tmpfile()
-            with io.open(self._local_tmpfile(), "r",
-                         encoding=gap_encoding) as fobj:
+            with open(self._local_tmpfile(), "r",
+                      encoding=gap_encoding) as fobj:
                 help = fobj.read()
             if pager:
                 from IPython.core.page import page